19 Original Export and Import

Running catexp.sql or catalog.sql

To use Export and Import, you must run the script catexp.sql or catalog.sql (which runs catexp.sql) after the database has been created or migrated to Oracle Database 10g.

The catexp.sql or catalog.sql script needs to be run only once on a database. The script performs the following tasks to prepare the database for export and import operations:

• Creates the necessary export and import views in the data dictionary

• Creates the EXP_FULL_DATABASE role

• Assigns all necessary privileges to the EXP_FULL_DATABASE and IMP_FULL_DATABASE roles

• Assigns EXP_FULL_DATABASE and IMP_FULL_DATABASE to the DBA role

• Records the version of catexp.sql that has been installed

Ensuring Sufficient Disk Space for Export Operations

Before you run Export, ensure that there is sufficient disk or tape storage space to write the export file. If there is not enough space, Export terminates with a write-failure error.

You can use table sizes to estimate the maximum space needed. You can find table sizes in the USER_SEGMENTS view of the Oracle data dictionary. The following query displays disk usage for all tables:

SELECT SUM(BYTES) FROM USER_SEGMENTS WHERE SEGMENT_TYPE='TABLE';

The result of the query does not include disk space used for data stored in LOB (large object) or VARRAY columns or in partitioned tables.

Verifying Access Privileges for Export and Import Operations

To use Export and Import, you must have the CREATE SESSION privilege on an Oracle database. This privilege belongs to the CONNECT role established during database creation. To export tables owned by another user, you must have the EXP_FULL_DATABASE role enabled. This role is granted to all database administrators (DBAs).

If you do not have the system privileges contained in the EXP_FULL_DATABASE role, you cannot export objects contained in another user's schema. For example, you cannot export a table in another user's schema, even if you created a synonym for it.

The following schema names are reserved and will not be processed by Export:

• ORDSYS

• MDSYS

• CTXSYS

• ORDPLUGINS

• LBACSYS

You can perform an import operation even if you did not create the export file. However, keep in mind that if the export file was created by a user with the EXP_FULL_DATABASE role, then you must have the IMP_FULL_DATABASE role to import it. Both of these roles are typically assigned to database administrators (DBAs).

Invoking Export and Import As SYSDBA

SYSDBA is used internally and has specialized functions; its behavior is not the same as for generalized users. Therefore, you should not typically need to invoke Export or Import as SYSDBA, except in the following situations:

• At the request of Oracle technical support

• When importing a transportable tablespace set

To invoke Export or Import as SYSDBA, use the following syntax (substitute exp for imp if you are using Export). Add any desired parameters or parameter filenames:

imp \'username/password AS SYSDBA\'

Optionally, you could also specify an instance name:

imp \'username/password@instance AS SYSDBA\' 
 

If either the username or password is omitted, you will be prompted you for it.

This example shows the entire connect string enclosed in quotation marks and backslashes. This is because the string, AS SYSDBA, contains a blank, a situation for which most operating systems require that the entire connect string be placed in quotation marks or marked as a literal by some method. Some operating systems also require that quotation marks on the command line be preceded by an escape character. In this example, backslashes are used as the escape character. If the backslashes were not present, the command-line parser that Export and Import use would not understand the quotation marks and would remove them.

Command-Line Entries

You can specify all valid parameters and their values from the command line using the following syntax:

exp username/password PARAMETER=value

or

exp username/password PARAMETER=(value1,value2,...,valuen)

The number of parameters cannot exceed the maximum length of a command line on the system. Note that the examples could use imp to invoke Import rather than exp to invoke Export.

Parameter Files

The information in this section applies to both Export and Import, but the examples show use of the Export command, exp.

You can specify all valid parameters and their values in a parameter file. Storing the parameters in a file allows them to be easily modified or reused, and is the recommended method for invoking Export. If you use different parameters for different databases, you can have multiple parameter files.

Create the parameter file using any flat file text editor. The command-line option PARFILE=filename tells Export to read the parameters from the specified file rather than from the command line. For example:

exp PARFILE=filename
exp username/password PARFILE=filename

The first example does not specify the username/password on the command line to illustrate that you can specify them in the parameter file, although, for security reasons, this is not recommended.

The syntax for parameter file specifications is one of the following:

PARAMETER=value
PARAMETER=(value)
PARAMETER=(value1, value2, ...)

The following example shows a partial parameter file listing:

FULL=y
FILE=dba.dmp
GRANTS=y
INDEXES=y
CONSISTENT=y

You can add comments to the parameter file by preceding them with the pound (#) sign. Export ignores all characters to the right of the pound (#) sign.

You can specify a parameter file at the same time that you are entering parameters on the command line. In fact, you can specify the same parameter in both places. The position of the PARFILE parameter and other parameters on the command line determines which parameters take precedence. For example, assume the parameter file params.dat contains the parameter INDEXES=y and Export is invoked with the following line:

exp username/password PARFILE=params.dat INDEXES=n

In this case, because INDEXES=n occurs after PARFILE=params.dat, INDEXES=n overrides the value of the INDEXES parameter in the parameter file.

Interactive Mode

If you prefer to be prompted for the value of each parameter, you can use the following syntax to start Export (or Import, if you specify imp) in interactive mode:

exp username/password

Commonly used parameters are displayed with a request for you to enter a value. The command-line interactive method does not provide prompts for all functionality and is provided only for backward compatibility. If you want to use an interactive interface, Oracle recommends that you use the Oracle Enterprise Manager Export or Import Wizard.

If you do not specify a username/password combination on the command line, then you are prompted for this information.

Getting Online Help

Export and Import both provide online help. Enter exp help=y on the command line to invoke Export help or imp help=y to invoke Import help.

Importing Grants

To import the privileges that a user has granted to others, the user initiating the import must either own the objects or have object privileges with the WITH GRANT OPTION. Table 19-2 shows the required conditions for the authorizations to be valid on the target system.

Importing Objects into Other Schemas

To import objects into another user's schema, you must have the IMP_FULL_DATABASE role enabled.

Importing System Objects

To import system objects from a full database export file, the IMP_FULL_DATABASE role must be enabled. The parameter FULL specifies that the following system objects are included in the import when the export file is a full export:

• Profiles

• Public database links

• Public synonyms

• Roles

• Rollback segment definitions

• Resource costs

• Foreign function libraries

• Context objects

• System procedural objects

• System audit options

• System privileges

• Tablespace definitions

• Tablespace quotas

• User definitions

• Directory aliases

• System event triggers

Processing Restrictions

The following restrictions apply when you process data with the Export and Import utilities:

• Java classes, resources, and procedures that are created using Enterprise JavaBeans (EJB) are not placed in the export file.

• Constraints that have been altered using the RELY keyword lose the RELY attribute when they are exported.

• When a type definition has evolved and then data referencing that evolved type is exported, the type definition on the import system must have evolved in the same manner.

• The table compression attribute of tables and partitions is preserved during export and import. However, the import process does not use the direct path API, hence the data will not be stored in the compressed format when imported.

Manually Creating Tables Before Importing Data

When you choose to create tables manually before importing data into them from an export file, you should use either the same table definition previously used or a compatible format. For example, although you can increase the width of columns and change their order, you cannot do the following:

• Add NOT NULL columns

• Change the datatype of a column to an incompatible datatype (LONG to NUMBER, for example)

• Change the definition of object types used in a table

• Change DEFAULT column values

  
  

  Note: When tables are manually created before data is imported, the CREATE TABLE statement in the export dump file will fail because the table already exists. To avoid this failure and continue loading data into the table, set the Import parameter IGNORE=y. Otherwise, no data will be loaded into the table because of the table creation error.

  
  

Disabling Referential Constraints

In the normal import order, referential constraints are imported only after all tables are imported. This sequence prevents errors that could occur if a referential integrity constraint exists for data that has not yet been imported.

These errors can still occur when data is loaded into existing tables. For example, if table emp has a referential integrity constraint on the mgr column that verifies that the manager number exists in emp, a legitimate employee row might fail the referential integrity constraint if the manager's row has not yet been imported.

When such an error occurs, Import generates an error message, bypasses the failed row, and continues importing other rows in the table. You can disable constraints manually to avoid this.

Referential constraints between tables can also cause problems. For example, if the emp table appears before the dept table in the export file, but a referential check exists from the emp table into the dept table, some of the rows from the emp table may not be imported due to a referential constraint violation.

To prevent errors like these, you should disable referential integrity constraints when importing data into existing tables.

Manually Ordering the Import

When the constraints are reenabled after importing, the entire table is checked, which may take a long time for a large table. If the time required for that check is too long, it may be beneficial to order the import manually.

To do so, perform several imports from an export file instead of one. First, import tables that are the targets of referential checks. Then, import the tables that reference them. This option works if tables do not reference each other in a circular fashion, and if a table does not reference itself.

Table-Level and Partition-Level Export

You can export tables, partitions, and subpartitions in the following ways:

• Table-level Export: exports all data from the specified tables

• Partition-level Export: exports only data from the specified source partitions or subpartitions

In all modes, partitioned data is exported in a format such that partitions or subpartitions can be imported selectively.

Table-Level and Partition-Level Import

You can import tables, partitions, and subpartitions in the following ways:

• Table-level Import: Imports all data from the specified tables in an export file.

• Partition-level Import: Imports only data from the specified source partitions or subpartitions.

You must set the parameter IGNORE=y when loading data into an existing table. See IGNORE for more information.

imp SYSTEM/password FILE=expdat.dmp FROMUSER=scott TABLES=b:py

imp scott/tiger FILE=expdat.dmp TABLES=(e:qc, e:qd) IGNORE=y

BUFFER

Default: operating system-dependent. See your Oracle operating system-specific documentation to determine the default value for this parameter.

Specifies the size, in bytes, of the buffer used to fetch rows. As a result, this parameter determines the maximum number of rows in an array fetched by Export. Use the following formula to calculate the buffer size:

buffer_size = rows_in_array * maximum_row_size

If you specify zero, the Export utility fetches only one row at a time.

Tables with columns of type LOBs, LONG, BFILE, REF, ROWID, LOGICAL ROWID, or DATE are fetched one row at a time.

CREATE TABLE sample (name varchar(30), weight number);

COMPRESS

Default: y

Specifies how Export and Import manage the initial extent for table data.

The default, COMPRESS=y, causes Export to flag table data for consolidation into one initial extent upon import. If extent sizes are large (for example, because of the PCTINCREASE parameter), the allocated space will be larger than the space required to hold the data.

If you specify COMPRESS=n, Export uses the current storage parameters, including the values of initial extent size and next extent size. The values of the parameters may be the values specified in the CREATE TABLE or ALTER TABLE statements or the values modified by the database system. For example, the NEXT extent size value may be modified if the table grows and if the PCTINCREASE parameter is nonzero.

CONSISTENT

Default: n

Specifies whether or not Export uses the SET TRANSACTION READ ONLY statement to ensure that the data seen by Export is consistent to a single point in time and does not change during the execution of the exp command. You should specify CONSISTENT=y when you anticipate that other applications will be updating the target data after an export has started.

If you use CONSISTENT=n, each table is usually exported in a single transaction. However, if a table contains nested tables, the outer table and each inner table are exported as separate transactions. If a table is partitioned, each partition is exported as a separate transaction.

Therefore, if nested tables and partitioned tables are being updated by other applications, the data that is exported could be inconsistent. To minimize this possibility, export those tables at a time when updates are not being done.

Table 19-4 shows a sequence of events by two users: user1 exports partitions in a table and user2 updates data in that table.

If the export uses CONSISTENT=y, none of the updates by user2 are written to the export file.

If the export uses CONSISTENT=n, the updates to TAB:P1 are not written to the export file. However, the updates to TAB:P2 are written to the export file, because the update transaction is committed before the export of TAB:P2 begins. As a result, the user2 transaction is only partially recorded in the export file, making it inconsistent.

If you use CONSISTENT=y and the volume of updates is large, the rollback segment usage will be large. In addition, the export of each table will be slower, because the rollback segment must be scanned for uncommitted transactions.

Keep in mind the following points about using CONSISTENT=y:

• CONSISTENT=y is unsupported for exports that are performed when you are connected as user SYS or you are using AS SYSDBA, or both.

• Export of certain metadata may require the use of the SYS schema within recursive SQL. In such situations, the use of CONSISTENT=y will be ignored. Oracle recommends that you avoid making metadata changes during an export process in which CONSISTENT=y is selected.

• To minimize the time and space required for such exports, you should export tables that need to remain consistent separately from those that do not. For example, export the emp and dept tables together in a consistent export, and then export the remainder of the database in a second pass.

• A "snapshot too old" error occurs when rollback space is used up, and space taken up by committed transactions is reused for new transactions. Reusing space in the rollback segment allows database integrity to be preserved with minimum space requirements, but it imposes a limit on the amount of time that a read-consistent image can be preserved.

  If a committed transaction has been overwritten and the information is needed for a read-consistent view of the database, a "snapshot too old" error results.

  To avoid this error, you should minimize the time taken by a read-consistent export. (Do this by restricting the number of objects exported and, if possible, by reducing the database transaction rate.) Also, make the rollback segment as large as possible.

  
  

  Note: Rollback segments will be deprecated in a future Oracle database release. Oracle recommends that you use automatic undo management instead.

  
  
  
  

  See Also: OBJECT_CONSISTENT

  
  

CONSTRAINTS

Default: y

Specifies whether or not the Export utility exports table constraints.

DIRECT

Default: n

Specifies the use of direct path Export.

Specifying DIRECT=y causes Export to extract data by reading the data directly, bypassing the SQL command-processing layer (evaluating buffer). This method can be much faster than a conventional path Export.

For information about direct path Exports, including security and performance considerations, see Invoking a Direct Path Export.

FEEDBACK

Default: 0 (zero)

Specifies that Export should display a progress meter in the form of a period for n number of rows exported. For example, if you specify FEEDBACK=10, Export displays a period each time 10 rows are exported. The FEEDBACK value applies to all tables being exported; it cannot be set individually for each table.

FILE

Default: expdat.dmp

Specifies the names of the export dump files. The default extension is .dmp, but you can specify any extension. Because Export supports multiple export files, you can specify multiple filenames to be used. For example:

exp scott/tiger FILE = dat1.dmp, dat2.dmp, dat3.dmp FILESIZE=2048

When Export reaches the value you have specified for the maximum FILESIZE, Export stops writing to the current file, opens another export file with the next name specified by the FILE parameter, and continues until complete or the maximum value of FILESIZE is again reached. If you do not specify sufficient export filenames to complete the export, Export will prompt you to provide additional filenames.

FILESIZE

Default: Data is written to one file until the maximum size, as specified in Table 19-5, is reached.

Export supports writing to multiple export files, and Import can read from multiple export files. If you specify a value (byte limit) for the FILESIZE parameter, Export will write only the number of bytes you specify to each dump file.

When the amount of data Export must write exceeds the maximum value you specified for FILESIZE, it will get the name of the next export file from the FILE parameter (see FILE for more information) or, if it has used all the names specified in the FILE parameter, it will prompt you to provide a new export filename. If you do not specify a value for FILESIZE (note that a value of 0 is equivalent to not specifying FILESIZE), then Export will write to only one file, regardless of the number of files specified in the FILE parameter.

The FILESIZE parameter has a maximum value equal to the maximum value that can be stored in 64 bits.

Table 19-5 shows that the maximum size for dump files depends on the operating system you are using and on the release of the Oracle database that you are using.

The maximum value that can be stored in a file is dependent on your operating system. You should verify this maximum value in your Oracle operating system-specific documentation before specifying FILESIZE. You should also ensure that the file size you specify for Export is supported on the system on which Import will run.

The FILESIZE value can also be specified as a number followed by KB (number of kilobytes). For example, FILESIZE=2KB is the same as FILESIZE=2048. Similarly, MB specifies megabytes (1024 * 1024) and GB specifies gigabytes (1024**3). B remains the shorthand for bytes; the number is not multiplied to obtain the final file size (FILESIZE=2048B is the same as FILESIZE=2048).

FLASHBACK_SCN

Default: none

Specifies the system change number (SCN) that Export will use to enable flashback. The export operation is performed with data consistent as of this specified SCN.

The following is an example of specifying an SCN. When the export is performed, the data will be consistent as of SCN 3482971.

> exp system/password FILE=exp.dmp FLASHBACK_SCN=3482971

FLASHBACK_TIME

Default: none

Enables you to specify a timestamp. Export finds the SCN that most closely matches the specified timestamp. This SCN is used to enable flashback. The export operation is performed with data consistent as of this SCN.

You can specify the time in any format that the DBMS_FLASHBACK.ENABLE_AT_TIME procedure accepts. This means that you can specify it in either of the following ways:

> exp system/password FILE=exp.dmp FLASHBACK_TIME="TIMESTAMP '2002-05-01 11:00:00'"

> exp system/password FILE=exp.dmp FLASHBACK_TIME="TO_TIMESTAMP('12-02-2001 14:35:00', 'DD-MM-YYYY HH24:MI:SS')"

Also, the old format, as shown in the following example, will continue to be accepted to ensure backward compatibility:

> exp system/password FILE=exp.dmp FLASHBACK_TIME="'2002-05-01 11:00:00'"

FULL

Default: n

Indicates that the export is a full database mode export (that is, it exports the entire database). Specify FULL=y to export in full database mode. You need to have the EXP_FULL_DATABASE role to export in this mode.

GRANTS

Default: y

Specifies whether or not the Export utility exports object grants. The object grants that are exported depend on whether you use full database mode or user mode. In full database mode, all grants on a table are exported. In user mode, only those granted by the owner of the table are exported. System privilege grants are always exported.

HELP

Default: none

Displays a description of the Export parameters. Enter exp help=y on the command line to invoke it.

INDEXES

Default: y

Specifies whether or not the Export utility exports indexes.

LOG

Default: none

Specifies a filename to receive informational and error messages. For example:

exp SYSTEM/password LOG=export.log

If you specify this parameter, messages are logged in the log file and displayed to the terminal display.

OBJECT_CONSISTENT

Default: n

Specifies whether or not the Export utility uses the SET TRANSACTION READ ONLY statement to ensure that the data exported is consistent to a single point in time and does not change during the export. If OBJECT_CONSISTENT is set to y, each object is exported in its own read-only transaction, even if it is partitioned. In contrast, if you use the CONSISTENT parameter, then there is only one read-only transaction.

OWNER

Default: none

Indicates that the export is a user-mode export and lists the users whose objects will be exported. If the user initiating the export is the database administrator (DBA), multiple users can be listed.

User-mode exports can be used to back up one or more database users. For example, a DBA may want to back up the tables of deleted users for a period of time. User mode is also appropriate for users who want to back up their own data or who want to move objects from one owner to another.

PARFILE

Default: none

Specifies a filename for a file that contains a list of Export parameters. For more information about using a parameter file, see Invoking Export and Import.

QUERY

Default: none

This parameter enables you to select a subset of rows from a set of tables when doing a table mode export. The value of the query parameter is a string that contains a WHERE clause for a SQL SELECT statement that will be applied to all tables (or table partitions) listed in the TABLE parameter.

For example, if user scott wants to export only those employees whose job title is SALESMAN and whose salary is less than 1600, he could do the following (this example is UNIX-based):

exp scott/tiger TABLES=emp QUERY=\"WHERE job=\'SALESMAN\' and sal \<1600\"

When executing this query, Export builds a SQL SELECT statement similar to the following:

SELECT * FROM emp WHERE job='SALESMAN' and sal <1600; 
 

The values specified for the QUERY parameter are applied to all tables (or table partitions) listed in the TABLE parameter. For example, the following statement will unload rows in both emp and bonus that match the query:

exp scott/tiger TABLES=emp,bonus QUERY=\"WHERE job=\'SALESMAN\' and sal\<1600\"
 

Again, the SQL statements that Export executes are similar to the following:

SELECT * FROM emp WHERE job='SALESMAN' and sal <1600;

SELECT * FROM bonus WHERE job='SALESMAN' and sal <1600;

If a table is missing the columns specified in the QUERY clause, an error message will be produced, and no rows will be exported for the offending table.

RECORDLENGTH

Default: operating system-dependent

Specifies the length, in bytes, of the file record. The RECORDLENGTH parameter is necessary when you must transfer the export file to another operating system that uses a different default value.

If you do not define this parameter, it defaults to your platform-dependent value for buffer size.

You can set RECORDLENGTH to any value equal to or greater than your system's buffer size. (The highest value is 64 KB.) Changing the RECORDLENGTH parameter affects only the size of data that accumulates before writing to the disk. It does not affect the operating system file block size.

RESUMABLE

Default: n

The RESUMABLE parameter is used to enable and disable resumable space allocation. Because this parameter is disabled by default, you must set RESUMABLE=y in order to use its associated parameters, RESUMABLE_NAME and RESUMABLE_TIMEOUT.

RESUMABLE_NAME

Default: 'User USERNAME (USERID), Session SESSIONID, Instance INSTANCEID'

The value for this parameter identifies the statement that is resumable. This value is a user-defined text string that is inserted in either the USER_RESUMABLE or DBA_RESUMABLE view to help you identify a specific resumable statement that has been suspended.

This parameter is ignored unless the RESUMABLE parameter is set to y to enable resumable space allocation.

RESUMABLE_TIMEOUT

Default: 7200 seconds (2 hours)

The value of the parameter specifies the time period during which an error must be fixed. If the error is not fixed within the timeout period, execution of the statement is terminated.

This parameter is ignored unless the RESUMABLE parameter is set to y to enable resumable space allocation.

ROWS

Default: y

Specifies whether or not the rows of table data are exported.

STATISTICS

Default: ESTIMATE

Specifies the type of database optimizer statistics to generate when the exported data is imported. Options are ESTIMATE, COMPUTE, and NONE. See the Import parameter STATISTICS and Importing Statistics.

In some cases, Export will place the precalculated statistics in the export file, as well as the ANALYZE statements to regenerate the statistics.

However, the precalculated optimizer statistics will not be used at export time if a table has columns with system-generated names.

The precalculated optimizer statistics are flagged as questionable at export time if:

• There are row errors while exporting

• The client character set or NCHAR character set does not match the server character set or NCHAR character set

• A QUERY clause is specified

• Only certain partitions or subpartitions are exported

  
  

  Note: Specifying ROWS=n does not preclude saving the precalculated statistics in the export file. This enables you to tune plan generation for queries in a nonproduction database using statistics from a production database.

  
  
  
  

  See Also: Oracle Database Concepts

  
  

TABLES

Default: none

Specifies that the export is a table-mode export and lists the table names and partition and subpartition names to export. You can specify the following when you specify the name of the table:

• schemaname specifies the name of the user's schema from which to export the table or partition. The schema names ORDSYS, MDSYS, CTXSYS, LBACSYS, and ORDPLUGINS are reserved by Export.

• tablename specifies the name of the table or tables to be exported. Table-level export lets you export entire partitioned or nonpartitioned tables. If a table in the list is partitioned and you do not specify a partition name, all its partitions and subpartitions are exported.

  The table name can contain any number of '%' pattern matching characters, which can each match zero or more characters in the table name against the table objects in the database. All the tables in the relevant schema that match the specified pattern are selected for export, as if the respective table names were explicitly specified in the parameter.

• partition_name indicates that the export is a partition-level Export. Partition-level Export lets you export one or more specified partitions or subpartitions within a table.

The syntax you use to specify the preceding is in the form:

schemaname.tablename:partition_name
schemaname.tablename:subpartition_name

If you use tablename:partition_name, the specified table must be partitioned, and partition_name must be the name of one of its partitions or subpartitions. If the specified table is not partitioned, the partition_name is ignored and the entire table is exported.

See Example Export Session Using Partition-Level Export for several examples of partition-level Exports.

TABLESPACES

Default: none

The TABLESPACES parameter specifies that all tables in the specified tablespace be exported to the Export dump file. This includes all tables contained in the list of tablespaces and all tables that have a partition located in the list of tablespaces. Indexes are exported with their tables, regardless of where the index is stored.

You must have the EXP_FULL_DATABASE role to use TABLESPACES to export all tables in the tablespace.

When TABLESPACES is used in conjunction with TRANSPORT_TABLESPACE=y, you can specify a limited list of tablespaces to be exported from the database to the export file.

TRANSPORT_TABLESPACE

Default: n

When specified as y, this parameter enables the export of transportable tablespace metadata.

TRIGGERS

Default: y

Specifies whether or not the Export utility exports triggers.

TTS_FULL_CHECK

Default: n

When TTS_FULL_CHECK is set to y, Export verifies that a recovery set (set of tablespaces to be recovered) has no dependencies (specifically, IN pointers) on objects outside the recovery set, and the reverse.

USERID (username/password)

Default: none

Specifies the username/password (and optional connect string) of the user performing the export. If you omit the password, Export will prompt you for it.

USERID can also be:

username/password AS SYSDBA

or

username/password@instance AS SYSDBA

If you connect as user SYS, you must also specify AS SYSDBA in the connect string. Your operating system may require you to treat AS SYSDBA as a special string, in which case the entire string would be enclosed in quotation marks. See Invoking Export and Import for more information.

VOLSIZE

Default: none

Specifies the maximum number of bytes in an export file on each volume of tape.

The VOLSIZE parameter has a maximum value equal to the maximum value that can be stored in 64 bits on your platform.

The VOLSIZE value can be specified as a number followed by KB (number of kilobytes). For example, VOLSIZE=2KB is the same as VOLSIZE=2048. Similarly, MB specifies megabytes (1024 * 1024) and GB specifies gigabytes (1024**3). B remains the shorthand for bytes; the number is not multiplied to get the final file size (VOLSIZE=2048B is the same as VOLSIZE=2048).

BUFFER

Default: operating system-dependent

The integer specified for BUFFER is the size, in bytes, of the buffer through which data rows are transferred.

BUFFER determines the number of rows in the array inserted by Import. The following formula gives an approximation of the buffer size that inserts a given array of rows:

buffer_size = rows_in_array * maximum_row_size

For tables containing LOBs or LONG, BFILE, REF, ROWID,UROWID, or TIMESTAMP columns, rows are inserted individually. The size of the buffer must be large enough to contain the entire row, except for LOB and LONG columns. If the buffer cannot hold the longest row in a table, Import attempts to allocate a larger buffer.

For DATE columns, two or more rows are inserted at once if the buffer is large enough.

COMMIT

Default: n

Specifies whether Import should commit after each array insert. By default, Import commits only after loading each table, and Import performs a rollback when an error occurs, before continuing with the next object.

If a table has nested table columns or attributes, the contents of the nested tables are imported as separate tables. Therefore, the contents of the nested tables are always committed in a transaction distinct from the transaction used to commit the outer table.

If COMMIT=n and a table is partitioned, each partition and subpartition in the Export file is imported in a separate transaction.

For tables containing LOBs, LONG, BFILE, REF, ROWID, or UROWID columns, array inserts are not done. If COMMIT=y, Import commits these tables after each row.

COMPILE

Default: y

Specifies whether or not Import should compile packages, procedures, and functions as they are created.

If COMPILE=n, these units are compiled on their first use. For example, packages that are used to build domain indexes are compiled when the domain indexes are created.

CONSTRAINTS

Default: y

Specifies whether or not table constraints are to be imported. The default is to import constraints. If you do not want constraints to be imported, you must set the parameter value to n.

Note that primary key constraints for index-organized tables (IOTs) and object tables are always imported.

DATAFILES

Default: none

When TRANSPORT_TABLESPACE is specified as y, use this parameter to list the datafiles to be transported into the database.

DESTROY

Default: n

Specifies whether or not the existing datafiles making up the database should be reused. That is, specifying DESTROY=y causes Import to include the REUSE option in the datafile clause of the SQL CREATE TABLESPACE statement, which causes Import to reuse the original database's datafiles after deleting their contents.

Note that the export file contains the datafile names used in each tablespace. If you specify DESTROY=y and attempt to create a second database on the same system (for testing or other purposes), the Import utility will overwrite the first database's datafiles when it creates the tablespace. In this situation you should use the default, DESTROY=n, so that an error occurs if the datafiles already exist when the tablespace is created. Also, when you need to import into the original database, you will need to specify IGNORE=y to add to the existing datafiles without replacing them.

FEEDBACK

Default: 0 (zero)

Specifies that Import should display a progress meter in the form of a period for n number of rows imported. For example, if you specify FEEDBACK=10, Import displays a period each time 10 rows have been imported. The FEEDBACK value applies to all tables being imported; it cannot be individually set for each table.

FILE

Default: expdat.dmp

Specifies the names of the export files to import. The default extension is .dmp. Because Export supports multiple export files (see the following description of the FILESIZE parameter), you may need to specify multiple filenames to be imported. For example:

imp scott/tiger IGNORE=y FILE = dat1.dmp, dat2.dmp, dat3.dmp FILESIZE=2048
 

You need not be the user who exported the export files; however, you must have read access to the files. If you were not the exporter of the export files, you must also have the IMP_FULL_DATABASE role granted to you.

FILESIZE

Default: operating system-dependent

Export supports writing to multiple export files, and Import can read from multiple export files. If, on export, you specify a value (byte limit) for the Export FILESIZE parameter, Export will write only the number of bytes you specify to each dump file. On import, you must use the Import parameter FILESIZE to tell Import the maximum dump file size you specified on export.

The FILESIZE value can be specified as a number followed by KB (number of kilobytes). For example, FILESIZE=2KB is the same as FILESIZE=2048. Similarly, MB specifies megabytes (1024 * 1024) and GB specifies gigabytes (1024**3). B remains the shorthand for bytes; the number is not multiplied to obtain the final file size (FILESIZE=2048B is the same as FILESIZE=2048).

For information about the maximum size of dump files, see Table 19-5.

FROMUSER

Default: none

A comma-delimited list of schemas to import. This parameter is relevant only to users with the IMP_FULL_DATABASE role. The parameter enables you to import a subset of schemas from an export file containing multiple schemas (for example, a full export dump file or a multischema, user-mode export dump file).

Schema names that appear inside function-based indexes, functions, procedures, triggers, type bodies, views, and so on, are not affected by FROMUSER or TOUSER processing. Only the name of the object is affected. After the import has completed, items in any TOUSER schema should be manually checked for references to old (FROMUSER) schemas, and corrected if necessary.

You will typically use FROMUSER in conjunction with the Import parameter TOUSER, which you use to specify a list of usernames whose schemas will be targets for import (see TOUSER). The user that you specify with TOUSER must exist in the target database prior to the import operation; otherwise an error is returned.

If you do not specify TOUSER, Import will do the following:

• Import objects into the FROMUSER schema if the export file is a full dump or a multischema, user-mode export dump file

• Create objects in the importer's schema (regardless of the presence of or absence of the FROMUSER schema on import) if the export file is a single-schema, user-mode export dump file created by an unprivileged user

  
  

  Note: Specifying FROMUSER=SYSTEM causes only schema objects belonging to user SYSTEM to be imported; it does not cause system objects to be imported.

  
  

FULL

Default: y

Specifies whether to import the entire export dump file.

GRANTS

Default: y

Specifies whether to import object grants.

By default, the Import utility imports any object grants that were exported. If the export was a user-mode export, the export file contains only first-level object grants (those granted by the owner).

If the export was a full database mode export, the export file contains all object grants, including lower-level grants (those granted by users given a privilege with the WITH GRANT OPTION). If you specify GRANTS=n, the Import utility does not import object grants. (Note that system grants are imported even if GRANTS=n.)

HELP

Default: none

Displays a description of the Import parameters. Enter imp HELP=y on the command line to invoke it.

IGNORE

Default: n

Specifies how object creation errors should be handled. If you accept the default, IGNORE=n, Import logs or displays object creation errors before continuing.

If you specify IGNORE=y, Import overlooks object creation errors when it attempts to create database objects, and continues without reporting the errors.

Note that only object creation errors are ignored; other errors, such as operating system, database, and SQL errors, are not ignored and may cause processing to stop.

In situations where multiple refreshes from a single export file are done with IGNORE=y, certain objects can be created multiple times (although they will have unique system-defined names). You can prevent this for certain objects (for example, constraints) by doing an import with CONSTRAINTS=n. If you do a full import with CONSTRAINTS=n, no constraints for any tables are imported.

If a table already exists and IGNORE=y, then rows are imported into existing tables without any errors or messages being given. You might want to import data into tables that already exist in order to use new storage parameters or because you have already created the table in a cluster.

If a table already exists and IGNORE=n, then errors are reported and the table is skipped with no rows inserted. Also, objects dependent on tables, such as indexes, grants, and constraints, will not be created.

INDEXES

Default: y

Specifies whether or not to import indexes. System-generated indexes such as LOB indexes, OID indexes, or unique constraint indexes are re-created by Import regardless of the setting of this parameter.

You can postpone all user-generated index creation until after Import completes, by specifying INDEXES=n.

If indexes for the target table already exist at the time of the import, Import performs index maintenance when data is inserted into the table.

INDEXFILE

Default: none

Specifies a file to receive index-creation statements.

When this parameter is specified, index-creation statements for the requested mode are extracted and written to the specified file, rather than used to create indexes in the database. No database objects are imported.

If the Import parameter CONSTRAINTS is set to y, Import also writes table constraints to the index file.

The file can then be edited (for example, to change storage parameters) and used as a SQL script to create the indexes.

To make it easier to identify the indexes defined in the file, the export file's CREATE TABLE statements and CREATE CLUSTER statements are included as comments.

Perform the following steps to use this feature:

1. Import using the INDEXFILE parameter to create a file of index-creation statements.

2. Edit the file, making certain to add a valid password to the connect strings.

3. Rerun Import, specifying INDEXES=n.

   (This step imports the database objects while preventing Import from using the index definitions stored in the export file.)

4. Execute the file of index-creation statements as a SQL script to create the index.

   The INDEXFILE parameter can be used only with the FULL=y, FROMUSER, TOUSER, or TABLES parameters.

LOG

Default: none

Specifies a file to receive informational and error messages. If you specify a log file, the Import utility writes all information to the log in addition to the terminal display.

PARFILE

Default: none

Specifies a filename for a file that contains a list of Import parameters. For more information about using a parameter file, see Parameter Files.

RECORDLENGTH

Default: operating system-dependent

Specifies the length, in bytes, of the file record. The RECORDLENGTH parameter is necessary when you must transfer the export file to another operating system that uses a different default value.

If you do not define this parameter, it defaults to your platform-dependent value for BUFSIZ.

You can set RECORDLENGTH to any value equal to or greater than your system's BUFSIZ. (The highest value is 64 KB.) Changing the RECORDLENGTH parameter affects only the size of data that accumulates before writing to the database. It does not affect the operating system file block size.

You can also use this parameter to specify the size of the Import I/O buffer.

RESUMABLE

Default: n

The RESUMABLE parameter is used to enable and disable resumable space allocation. Because this parameter is disabled by default, you must set RESUMABLE=y in order to use its associated parameters, RESUMABLE_NAME and RESUMABLE_TIMEOUT.

RESUMABLE_NAME

Default: 'User USERNAME (USERID), Session SESSIONID, Instance INSTANCEID'

The value for this parameter identifies the statement that is resumable. This value is a user-defined text string that is inserted in either the USER_RESUMABLE or DBA_RESUMABLE view to help you identify a specific resumable statement that has been suspended.

This parameter is ignored unless the RESUMABLE parameter is set to y to enable resumable space allocation.

RESUMABLE_TIMEOUT

Default: 7200 seconds (2 hours)

The value of the parameter specifies the time period during which an error must be fixed. If the error is not fixed within the timeout period, execution of the statement is terminated.

This parameter is ignored unless the RESUMABLE parameter is set to y to enable resumable space allocation.

ROWS

Default: y

Specifies whether or not to import the rows of table data.

SHOW

Default: n

When SHOW=y, the contents of the export dump file are listed to the display and not imported. The SQL statements contained in the export are displayed in the order in which Import will execute them.

The SHOW parameter can be used only with the FULL=y, FROMUSER, TOUSER, or TABLES parameter.

SKIP_UNUSABLE_INDEXES

Default: the value of the Oracle database configuration parameter, SKIP_UNUSABLE_INDEXES, as specified in the initialization parameter file

Both Import and the Oracle database provide a SKIP_UNUSABLE_INDEXES parameter. The Import SKIP_UNUSABLE_INDEXES parameter is specified at the Import command line. The Oracle database SKIP_UNUSABLE_INDEXES parameter is specified as a configuration parameter in the initialization parameter file. It is important to understand how they affect each other.

If you do not specify a value for SKIP_UNUSABLE_INDEXES at the Import command line, then Import uses the database setting for the SKIP_UNUSABLE_INDEXES configuration parameter, as specified in the initialization parameter file.

If you do specify a value for SKIP_UNUSABLE_INDEXES at the Import command line, it overrides the value of the SKIP_UNUSABLE_INDEXES configuration parameter in the initialization parameter file.

A value of y means that Import will skip building indexes that were set to the Index Unusable state (by either system or user). Other indexes (not previously set to Index Unusable) continue to be updated as rows are inserted.

This parameter enables you to postpone index maintenance on selected index partitions until after row data has been inserted. You then have the responsibility to rebuild the affected index partitions after the Import.

You can use the INDEXFILE parameter in conjunction with INDEXES=n to provide the SQL scripts for re-creating the index. If the SKIP_UNUSABLE_INDEXES parameter is not specified, row insertions that attempt to update unusable indexes will fail.

STATISTICS

Default: ALWAYS

Specifies what is done with the database optimizer statistics at import time.

The options are:

• ALWAYS

  Always import database optimizer statistics regardless of whether or not they are questionable.

• NONE

  Do not import or recalculate the database optimizer statistics.

• SAFE

  Import database optimizer statistics only if they are not questionable. If they are questionable, recalculate the optimizer statistics.

• RECALCULATE

  Do not import the database optimizer statistics. Instead, recalculate them on import. This requires that the original export operation that created the dump file must have generated the necessary ANALYZE statements (that is, the export was not performed with STATISTICS=NONE). These ANALYZE statements are included in the dump file and used by the import operation for recalculation of the table's statistics.

  
  

  See Also: Oracle Database Concepts for more information about the optimizer and the statistics it uses Importing Statistics

  
  

STREAMS_CONFIGURATION

Default: y

Specifies whether or not to import any general Streams metadata that may be present in the export dump file.

STREAMS_INSTANTIATION

Default: n

Specifies whether or not to import Streams instantiation metadata that may be present in the export dump file. Specify y if the import is part of an instantiation in a Streams environment.

TABLES

Default: none

Specifies that the import is a table-mode import and lists the table names and partition and subpartition names to import. Table-mode import lets you import entire partitioned or nonpartitioned tables. The TABLES parameter restricts the import to the specified tables and their associated objects, as listed in Table 19-3. You can specify the following values for the TABLES parameter:

• tablename specifies the name of the table or tables to be imported. If a table in the list is partitioned and you do not specify a partition name, all its partitions and subpartitions are imported. To import all the exported tables, specify an asterisk (*) as the only table name parameter.

  tablename can contain any number of '%' pattern matching characters, which can each match zero or more characters in the table names in the export file. All the tables whose names match all the specified patterns of a specific table name in the list are selected for import. A table name in the list that consists of all pattern matching characters and no partition name results in all exported tables being imported.

• partition_name and subpartition_name let you restrict the import to one or more specified partitions or subpartitions within a partitioned table.

The syntax you use to specify the preceding is in the form:

tablename:partition_name

tablename:subpartition_name

If you use tablename:partition_name, the specified table must be partitioned, and partition_name must be the name of one of its partitions or subpartitions. If the specified table is not partitioned, the partition_name is ignored and the entire table is imported.

The number of tables that can be specified at the same time is dependent on command-line limits.

As the export file is processed, each table name in the export file is compared against each table name in the list, in the order in which the table names were specified in the parameter. To avoid ambiguity and excessive processing time, specific table names should appear at the beginning of the list, and more general table names (those with patterns) should appear at the end of the list.

Although you can qualify table names with schema names (as in scott.emp) when exporting, you cannot do so when importing. In the following example, the TABLES parameter is specified incorrectly:

imp SYSTEM/password TABLES=(jones.accts, scott.emp, scott.dept)

The valid specification to import these tables is as follows:

imp SYSTEM/password FROMUSER=jones TABLES=(accts)
imp SYSTEM/password FROMUSER=scott TABLES=(emp,dept)

For a more detailed example, see Example Import Using Pattern Matching to Import Various Tables.

TABLES=\(emp,dept\)

TABLESPACES

Default: none

When TRANSPORT_TABLESPACE is specified as y, use this parameter to list the tablespaces to be transported into the database. If there is more than one tablespace in the export file, you must specify all of them as part of the import operation.

See TRANSPORT_TABLESPACE for more information.

TOID_NOVALIDATE

Default: none

When you import a table that references a type, but a type of that name already exists in the database, Import attempts to verify that the preexisting type is, in fact, the type used by the table (rather than a different type that just happens to have the same name).

To do this, Import compares the type's unique identifier (TOID) with the identifier stored in the export file. Import will not import the table rows if the TOIDs do not match.

In some situations, you may not want this validation to occur on specified types (for example, if the types were created by a cartridge installation). You can use the TOID_NOVALIDATE parameter to specify types to exclude from TOID comparison.

The syntax is as follows:

TOID_NOVALIDATE=([schemaname.]typename [, ...])

For example:

imp scott/tiger TABLE=jobs TOID_NOVALIDATE=typ1
imp scott/tiger TABLE=salaries TOID_NOVALIDATE=(fred.typ0,sally.typ2,typ3)

If you do not specify a schema name for the type, it defaults to the schema of the importing user. For example, in the first preceding example, the type typ1 defaults to scott.typ1.

Note that TOID_NOVALIDATE deals only with table column types. It has no effect on table types.

The output of a typical import with excluded types would contain entries similar to the following:

[...]
. importing IMP3's objects into IMP3
. . skipping TOID validation on type IMP2.TOIDTYP0
. . importing table                  "TOIDTAB3"          
[...]

TOUSER

Default: none

Specifies a list of user names whose schemas will be targets for Import. The user names must exist prior to the import operation; otherwise an error is returned. The IMP_FULL_DATABASE role is required to use this parameter. To import to a different schema than the one that originally contained the object, specify TOUSER. For example:

imp SYSTEM/password FROMUSER=scott TOUSER=joe TABLES=emp

If multiple schemas are specified, the schema names are paired. The following example imports scott's objects into joe's schema, and fred's objects into ted's schema:

imp SYSTEM/password FROMUSER=scott,fred TOUSER=joe,ted

If the FROMUSER list is longer than the TOUSER list, the remaining schemas will be imported into either the FROMUSER schema, or into the importer's schema, based on normal defaulting rules. You can use the following syntax to ensure that any extra objects go into the TOUSER schema:

imp SYSTEM/password FROMUSER=scott,adams TOUSER=ted,ted

Note that user ted is listed twice.

TRANSPORT_TABLESPACE

Default: n

When specified as y, instructs Import to import transportable tablespace metadata from an export file.

TTS_OWNERS

Default: none

When TRANSPORT_TABLESPACE is specified as y, use this parameter to list the users who own the data in the transportable tablespace set.

See TRANSPORT_TABLESPACE.

USERID (username/password)

Default: none

Specifies the username/password (and optional connect string) of the user performing the import.

USERID can also be:

username/password AS SYSDBA

or

username/password@instance

or

username/password@instance AS SYSDBA

If you connect as user SYS, you must also specify AS SYSDBA in the connect string. Your operating system may require you to treat AS SYSDBA as a special string, in which case the entire string would be enclosed in quotation marks.

VOLSIZE

Default: none

Specifies the maximum number of bytes in a dump file on each volume of tape.

The VOLSIZE parameter has a maximum value equal to the maximum value that can be stored in 64 bits on your platform.

The VOLSIZE value can be specified as number followed by KB (number of kilobytes). For example, VOLSIZE=2KB is the same as VOLSIZE=2048. Similarly, MB specifies megabytes (1024 * 1024) and GB specifies gigabytes (1024**3). The shorthand for bytes remains B; the number is not multiplied to get the final file size (VOLSIZE=2048B is the same as VOLSIZE=2048).

Example Export Session in Full Database Mode

Only users with the DBA role or the EXP_FULL_DATABASE role can export in full database mode. In this example, an entire database is exported to the file dba.dmp with all GRANTS and all data.

Parameter File Method

> exp SYSTEM/password PARFILE=params.dat

The params.dat file contains the following information:

FILE=dba.dmp
GRANTS=y
FULL=y
ROWS=y

Command-Line Method

> exp SYSTEM/password FULL=y FILE=dba.dmp GRANTS=y ROWS=y

Export Messages

Information is displayed about the release of Export you are using and the release of Oracle Database that you are connected to. Status messages are written out as the entire database is exported. A final completion message is returned when the export completes successfully, without warnings.

Example Export Session in User Mode

User-mode exports can be used to back up one or more database users. For example, a DBA may want to back up the tables of deleted users for a period of time. User mode is also appropriate for users who want to back up their own data or who want to move objects from one owner to another. In this example, user scott is exporting his own tables.

Parameter File Method

> exp scott/tiger PARFILE=params.dat

The params.dat file contains the following information:

FILE=scott.dmp
OWNER=scott
GRANTS=y
ROWS=y
COMPRESS=y

Command-Line Method

> exp scott/tiger FILE=scott.dmp OWNER=scott GRANTS=y ROWS=y COMPRESS=y 

Export Messages

Information is displayed about the release of Export you are using and the release of Oracle Database that you are connected to. Then, status messages similar to the following are shown:

.
.
. about to export SCOTT's tables via Conventional Path ...
. . exporting table                          BONUS          0 rows exported
. . exporting table                           DEPT          4 rows exported
. . exporting table                            EMP         14 rows exported
. . exporting table                       SALGRADE          5 rows exported
.
.
.
Export terminated successfully without warnings.

Example Export Sessions in Table Mode

In table mode, you can export table data or the table definitions. (If no rows are exported, the CREATE TABLE statement is placed in the export file, with grants and indexes, if they are specified.)

A user with the EXP_FULL_DATABASE role can use table mode to export tables from any user's schema by specifying TABLES=schemaname.tablename.

If schemaname is not specified, Export defaults to the previous schema name from which an object was exported. If there is not a previous object, Export defaults to the exporter's schema. In the following example, Export defaults to the SYSTEM schema for table a and to scott for table c:

> exp SYSTEM/password TABLES=(a, scott.b, c, mary.d)

A user with the EXP_FULL_DATABASE role can also export dependent objects that are owned by other users. A nonprivileged user can export only dependent objects for the specified tables that the user owns.

Exports in table mode do not include cluster definitions. As a result, the data is exported as unclustered tables. Thus, you can use table mode to uncluster tables.

> exp SYSTEM/password PARFILE=params.dat

FILE=expdat.dmp
TABLES=(scott.emp,blake.dept)
GRANTS=y
INDEXES=y

> exp SYSTEM/password FILE=expdat.dmp TABLES=(scott.emp,blake.dept) GRANTS=y INDEXES=y

.
.
.
About to export specified tables via Conventional Path ...
Current user changed to SCOTT
. . exporting table                            EMP         14 rows exported
Current user changed to BLAKE
. . exporting table                           DEPT          8 rows exported
Export terminated successfully without warnings.

> exp blake/paper PARFILE=params.dat

FILE=blake.dmp
TABLES=(dept,manager)
ROWS=y
COMPRESS=y

> exp blake/paper FILE=blake.dmp TABLES=(dept, manager) ROWS=y COMPRESS=y

.
.
.

About to export specified tables via Conventional Path ...
. . exporting table                           DEPT          8 rows exported
. . exporting table                        MANAGER          4 rows exported
Export terminated successfully without warnings.

> exp SYSTEM/password PARFILE=params.dat

FILE=misc.dmp
TABLES=(scott.%P%,blake.%,scott.%S%)

> exp SYSTEM/password FILE=misc.dmp TABLES=(scott.%P%,blake.%,scott.%S%)

.
.
.
About to export specified tables via Conventional Path ...
Current user changed to SCOTT
. . exporting table                           DEPT          4 rows exported
. . exporting table                            EMP         14 rows exported
Current user changed to BLAKE
. . exporting table                           DEPT          8 rows exported
. . exporting table                        MANAGER          4 rows exported
Current user changed to SCOTT
. . exporting table                          BONUS          0 rows exported
. . exporting table                       SALGRADE          5 rows exported
Export terminated successfully without warnings.

Example Export Session Using Partition-Level Export

In partition-level Export, you can specify the partitions and subpartitions of a table that you want to export.

> exp scott/tiger PARFILE=params.dat

TABLES=(emp)
ROWS=y

> exp scott/tiger TABLES=emp rows=y

.
.
.
About to export specified tables via Conventional Path ...
. . exporting table                            EMP
. . exporting partition                              M          8 rows exported
. . exporting partition                              Z          6 rows exported
Export terminated successfully without warnings.

> exp scott/tiger PARFILE=params.dat

TABLES=(emp:m)
ROWS=y

> exp scott/tiger TABLES=emp:m rows=y

.
.
.
About to export specified tables via Conventional Path ...
. . exporting table                            EMP
. . exporting partition                              M          8 rows exported
Export terminated successfully without warnings.

> exp scott/tiger PARFILE=params.dat

TABLES=(emp:m,emp:sp4)
ROWS=y

> exp scott/tiger TABLES=(emp:m, emp:sp4) ROWS=y

.
.
.
About to export specified tables via Conventional Path ...
. . exporting table                            EMP
. . exporting composite partition                    M
. . exporting subpartition                         SP1          1 rows exported
. . exporting subpartition                         SP2          3 rows exported
. . exporting composite partition                    Z
. . exporting subpartition                         SP4          1 rows exported
Export terminated successfully without warnings.

Example Import of Selected Tables for a Specific User

In this example, using a full database export file, an administrator imports the dept and emp tables into the scott schema.

Parameter File Method

> imp SYSTEM/password PARFILE=params.dat

The params.dat file contains the following information:

FILE=dba.dmp
SHOW=n
IGNORE=n
GRANTS=y
FROMUSER=scott
TABLES=(dept,emp)

Command-Line Method

> imp SYSTEM/password FILE=dba.dmp FROMUSER=scott TABLES=(dept,emp)

Import Messages

Information is displayed about the release of Import you are using and the release of Oracle Database that you are connected to. Then, status messages similar to the following are shown:

.
.
.
Export file created by EXPORT:V10.00.00 via conventional path
import done in WE8DEC character set and AL16UTF16 NCHAR character set
. importing SCOTT's objects into SCOTT
. . importing table                         "DEPT"          4 rows imported
. . importing table                          "EMP"         14 rows imported
Import terminated successfully without warnings.

Example Import of Tables Exported by Another User

This example illustrates importing the unit and manager tables from a file exported by blake into the scott schema.

Parameter File Method

> imp SYSTEM/password PARFILE=params.dat

The params.dat file contains the following information:

FILE=blake.dmp
SHOW=n
IGNORE=n
GRANTS=y
ROWS=y
FROMUSER=blake
TOUSER=scott
TABLES=(unit,manager)

Command-Line Method

> imp SYSTEM/password FROMUSER=blake TOUSER=scott FILE=blake.dmp - TABLES=(unit,manager)

Import Messages

Information is displayed about the release of Import you are using and the release of Oracle Database that you are connected to. Then, status messages similar to the following are shown:

.
.
.
Warning: the objects were exported by BLAKE, not by you

import done in WE8DEC character set and AL16UTF16 NCHAR character set
. . importing table                         "UNIT"          4 rows imported
. . importing table                      "MANAGER"          4 rows imported
Import terminated successfully without warnings.

Example Import of Tables from One User to Another

In this example, a database administrator (DBA) imports all tables belonging to scott into user blake's account.

Parameter File Method

> imp SYSTEM/password PARFILE=params.dat

The params.dat file contains the following information:

FILE=scott.dmp
FROMUSER=scott
TOUSER=blake
TABLES=(*)

Command-Line Method

> imp SYSTEM/password FILE=scott.dmp FROMUSER=scott TOUSER=blake TABLES=(*)

Import Messages

Information is displayed about the release of Import you are using and the release of Oracle Database that you are connected to. Then, status messages similar to the following are shown:

.
.
.
Warning: the objects were exported by SCOTT, not by you

import done in WE8DEC character set and AL16UTF16 NCHAR character set
. importing SCOTT's objects into BLAKE
. . importing table                        "BONUS"          0 rows imported
. . importing table                         "DEPT"          4 rows imported
. . importing table                          "EMP"         14 rows imported
. . importing table                     "SALGRADE"          5 rows imported
Import terminated successfully without warnings.

Example Import Session Using Partition-Level Import

This section describes an import of a table with multiple partitions, a table with partitions and subpartitions, and repartitioning a table on different columns.

> exp scott/tiger TABLES=emp FILE=exmpexp.dat ROWS=y

.
.
.
About to export specified tables via Conventional Path ...
. . exporting table                            EMP
. . exporting partition                             P1          7 rows exported
. . exporting partition                             P2         12 rows exported
. . exporting partition                             P3          3 rows exported
Export terminated successfully without warnings.

> imp scott/tiger TABLES=(emp:p1,emp:p3) FILE=exmpexp.dat ROWS=y 

.
.
.
Export file created by EXPORT:V10.00.00 via conventional path
import done in WE8DEC character set and AL16UTF16 NCHAR character set
. importing SCOTT's objects into SCOTT
. . importing partition                     "EMP":"P1"          7 rows imported
. . importing partition                     "EMP":"P3"          3 rows imported
Import terminated successfully without warnings.

> exp scott/tiger TABLES=emp FILE=exmpexp.dat ROWS=y 

.
.
.
About to export specified tables via Conventional Path ...
. . exporting table                            EMP
. . exporting composite partition                   P1
. . exporting subpartition                      P1_SP1          2 rows exported
. . exporting subpartition                      P1_SP2         10 rows exported
. . exporting subpartition                      P1_SP3          7 rows exported
. . exporting composite partition                   P2
. . exporting subpartition                      P2_SP1          4 rows exported
. . exporting subpartition                      P2_SP2          2 rows exported
Export terminated successfully without warnings.

> imp scott/tiger TABLES=(emp:p1_sp2,emp:p1_sp3,emp:p2) FILE=exmpexp.dat ROWS=y  

.
.
.
. importing SCOTT's objects into SCOTT
. . importing subpartition              "EMP":"P1_SP2"         10 rows imported
. . importing subpartition              "EMP":"P1_SP3"          7 rows imported
. . importing subpartition              "EMP":"P2_SP1"          4 rows imported
. . importing subpartition              "EMP":"P2_SP2"          2 rows imported
Import terminated successfully without warnings.

> exp scott/tiger table=emp file=empexp.dat 
.
.
.

About to export specified tables via Conventional Path ...
. . exporting table                            EMP
. . exporting partition                        EMP_LOW          4 rows exported
. . exporting partition                       EMP_HIGH         10 rows exported
Export terminated successfully without warnings.

SQL> connect scott/tiger
Connected.
SQL> drop table emp cascade constraints;
Statement processed.
SQL> create table emp
  2    (
  3    empno    number(4) not null,
  4    ename    varchar2(10),
  5    job      varchar2(9),
  6    mgr      number(4),
  7    hiredate date,
  8    sal      number(7,2),
  9    comm     number(7,2),
 10    deptno   number(2)
 11    )
 12 partition by range (deptno)
 13   (
 14   partition dept_low values less than (15)
 15     tablespace tbs_1,
 16   partition dept_mid values less than (25)
 17     tablespace tbs_2,
 18   partition dept_high values less than (35)
 19     tablespace tbs_3
 20   );
Statement processed.
SQL> exit

> imp scott/tiger tables=emp file=empexp.dat ignore=y
.
.
.
import done in WE8DEC character set and AL16UTF16 NCHAR character set
. importing SCOTT's objects into SCOTT
. . importing partition                "EMP":"EMP_LOW"          4 rows imported
. . importing partition               "EMP":"EMP_HIGH"         10 rows imported
Import terminated successfully without warnings.

SQL> connect scott/tiger
Connected.
SQL> select empno, deptno from emp partition (dept_low);
EMPNO      DEPTNO    
---------- ----------
      7782         10
      7839         10
      7934         10
3 rows selected.
SQL> select empno, deptno from emp partition (dept_mid);
EMPNO      DEPTNO    
---------- ----------
      7369         20
      7566         20
      7788         20
      7876         20
      7902         20
5 rows selected.
SQL> select empno, deptno from emp partition (dept_high);
EMPNO      DEPTNO    
---------- ----------
      7499         30
      7521         30
      7654         30
      7698         30
      7844         30
      7900         30
6 rows selected.
SQL> exit;

Example Import Using Pattern Matching to Import Various Tables

In this example, pattern matching is used to import various tables for user scott.

Parameter File Method

imp SYSTEM/password PARFILE=params.dat

The params.dat file contains the following information:

FILE=scott.dmp
IGNORE=n
GRANTS=y
ROWS=y
FROMUSER=scott
TABLES=(%d%,b%s)

Command-Line Method

imp SYSTEM/password FROMUSER=scott FILE=scott.dmp TABLES=(%d%,b%s)

Import Messages

Information is displayed about the release of Import you are using and the release of Oracle Database that you are connected to. Then, status messages similar to the following are shown:

.
.
.
import done in US7ASCII character set and AL16UTF16 NCHAR character set
import server uses JA16SJIS character set (possible charset conversion)
. importing SCOTT's objects into SCOTT
. . importing table                  "BONUS"          0 rows imported
. . importing table                   "DEPT"          4 rows imported
. . importing table               "SALGRADE"          5 rows imported
Import terminated successfully without warnings.

Log File

You can capture all Export and Import messages in a log file, either by using the LOG parameter or, for those systems that permit it, by redirecting the output to a file. A log of detailed information is written about successful unloads and loads and any errors that may have occurred.

Warning Messages

Export and Import do not terminate after recoverable errors. For example, if an error occurs while exporting a table, Export displays (or logs) an error message, skips to the next table, and continues processing. These recoverable errors are known as warnings.

Export and Import also issue warnings when invalid objects are encountered.

For example, if a nonexistent table is specified as part of a table-mode Export, the Export utility exports all other tables. Then it issues a warning and terminates successfully.

Nonrecoverable Error Messages

Some errors are nonrecoverable and terminate the Export or Import session. These errors typically occur because of an internal problem or because a resource, such as memory, is not available or has been exhausted. For example, if the catexp.sql script is not executed, Export issues the following nonrecoverable error message:

EXP-00024: Export views not installed, please notify your DBA

Completion Messages

When an export or import completes without errors, a message to that effect is displayed, for example:

Export terminated successfully without warnings

If one or more recoverable errors occurs but the job continues to completion, a message similar to the following is displayed:

Export terminated successfully with warnings

If a nonrecoverable error occurs, the job terminates immediately and displays a message stating so, for example:

Export terminated unsuccessfully

Transporting Export Files Across a Network

Because the export file is in binary format, use a protocol that supports binary transfers to prevent corruption of the file when you transfer it across a network. For example, use FTP or a similar file transfer protocol to transmit the file in binary mode. Transmitting export files in character mode causes errors when the file is imported.

Exporting and Importing with Oracle Net

With Oracle Net, you can perform exports and imports over a network. For example, if you run Export locally, you can write data from a remote Oracle database into a local export file. If you run Import locally, you can read data into a remote Oracle database.

To use Export or Import with Oracle Net, include the connection qualifier string @connect_string when entering the username/password in the exp or imp command. For the exact syntax of this clause, see the user's guide for your Oracle Net protocol.

User Data

The Export utility always exports user data, including Unicode data, in the character sets of the Export server. (Character sets are specified at database creation.) If the character sets of the source database are different than the character sets of the import database, a single conversion is performed to automatically convert the data to the character sets of the Import server.

CREATE TABLE partlist 
   ( 
   part     VARCHAR2(10), 
   partno   NUMBER(2) 
   ) 
PARTITION BY RANGE (part) 
  ( 
  PARTITION part_low VALUES LESS THAN ('Z') 
    TABLESPACE tbs_1, 
  PARTITION part_mid VALUES LESS THAN ('z') 
    TABLESPACE tbs_2, 
  PARTITION part_high VALUES LESS THAN (MAXVALUE) 
    TABLESPACE tbs_3 
  );

Data Definition Language (DDL)

Up to three character set conversions may be required for data definition language (DDL) during an export/import operation:

1. Export writes export files using the character set specified in the NLS_LANG environment variable for the user session. A character set conversion is performed if the value of NLS_LANG differs from the database character set.

2. If the export file's character set is different than the import user session character set, then Import converts the character set to its user session character set. Import can only perform this conversion for single-byte character sets. This means that for multibyte character sets, the import file's character set must be identical to the export file's character set.

3. A final character set conversion may be performed if the target database's character set is different from the character set used by the import user session.

To minimize data loss due to character set conversions, ensure that the export database, the export user session, the import user session, and the import database all use the same character set.

Single-Byte Character Sets and Export and Import

Some 8-bit characters can be lost (that is, converted to 7-bit equivalents) when you import an 8-bit character set export file. This occurs if the system on which the import occurs has a native 7-bit character set, or the NLS_LANG operating system environment variable is set to a 7-bit character set. Most often, this is apparent when accented characters lose the accent mark.

To avoid this unwanted conversion, you can set the NLS_LANG operating system environment variable to be that of the export file character set.

Multibyte Character Sets and Export and Import

During character set conversion, any characters in the export file that have no equivalent in the target character set are replaced with a default character. (The default character is defined by the target character set.) To guarantee 100% conversion, the target character set must be a superset (or equivalent) of the source character set.

Snapshot Log

The snapshot log in a dump file is imported if the master table already exists for the database to which you are importing and it has a snapshot log.

When a ROWID snapshot log is exported, ROWIDs stored in the snapshot log have no meaning upon import. As a result, each ROWID snapshot's first attempt to do a fast refresh fails, generating an error indicating that a complete refresh is required.

To avoid the refresh error, do a complete refresh after importing a ROWID snapshot log. After you have done a complete refresh, subsequent fast refreshes will work properly. In contrast, when a primary key snapshot log is exported, the values of the primary keys do retain their meaning upon import. Therefore, primary key snapshots can do a fast refresh after the import.

Snapshots

A snapshot that has been restored from an export file has reverted to a previous state. On import, the time of the last refresh is imported as part of the snapshot table definition. The function that calculates the next refresh time is also imported.

Each refresh leaves a signature. A fast refresh uses the log entries that date from the time of that signature to bring the snapshot up to date. When the fast refresh is complete, the signature is deleted and a new signature is created. Any log entries that are not needed to refresh other snapshots are also deleted (all log entries with times before the earliest remaining signature).

The OPTIMAL Parameter

The storage parameter OPTIMAL for rollback segments is not preserved during export and import.

Storage Parameters for OID Indexes and LOB Columns

Tables are exported with their current storage parameters. For object tables, the OIDINDEX is created with its current storage parameters and name, if given. For tables that contain LOB, VARRAY, or OPAQUE type columns, LOB, VARRAY, or OPAQUE type data is created with their current storage parameters.

If you alter the storage parameters of existing tables prior to export, the tables are exported using those altered storage parameters. Note, however, that storage parameters for LOB data cannot be altered prior to export (for example, chunk size for a LOB column, whether a LOB column is CACHE or NOCACHE, and so forth).

Note that LOB data might not reside in the same tablespace as the containing table. The tablespace for that data must be read/write at the time of import or the table will not be imported.

If LOB data resides in a tablespace that does not exist at the time of import, or the user does not have the necessary quota in that tablespace, the table will not be imported. Because there can be multiple tablespace clauses, including one for the table, Import cannot determine which tablespace clause caused the error.

Overriding Storage Parameters

Before using the Import utility to import data, you may want to create large tables with different storage parameters. If so, you must specify IGNORE=y on the command line or in the parameter file.

The Export COMPRESS Parameter

By default at export time, storage parameters are adjusted to consolidate all data into its initial extent. To preserve the original size of an initial extent, you must specify at export time that extents are not to be consolidated (by setting COMPRESS=n). See COMPRESS.

Conventional Path Export Versus Direct Path Export

Export provides two methods for exporting table data:

• Conventional path Export

• Direct path Export

Conventional path Export uses the SQL SELECT statement to extract data from tables. Data is read from disk into a buffer cache, and rows are transferred to the evaluating buffer. The data, after passing expression evaluation, is transferred to the Export client, which then writes the data into the export file.

Direct path Export is much faster than conventional path Export because data is read from disk into the buffer cache and rows are transferred directly to the Export client. The evaluating buffer (that is, the SQL command-processing layer) is bypassed. The data is already in the format that Export expects, thus avoiding unnecessary data conversion. The data is transferred to the Export client, which then writes the data into the export file.

Invoking a Direct Path Export

To use direct path Export, specify the DIRECT=y parameter on the command line or in the parameter file. The default is DIRECT=n, which extracts the table data using the conventional path. The rest of this section discusses the following topics:

• Security Considerations for Direct Path Exports

• Performance Considerations for Direct Path Exports

• Restrictions for Direct Path Exports

  
  

  Note: When you export a table in direct path, be sure that no other transaction is updating the same table, and that the size of the rollback segment is sufficient. Otherwise, you may receive the following error: ORA-01555 snapshot too old; rollback segment number string with name "string" too small This will cause the export to terminate unsuccessfully.

  
  

Exporting from a Read-Only Database

To extract metadata from a source database, Export uses queries that contain ordering clauses (sort operations). For these queries to succeed, the user performing the export must be able to allocate sort segments. For these sort segments to be allocated in a read-only database, the user's temporary tablespace should be set to point at a temporary, locally managed tablespace.

Considerations When Exporting Database Objects

The following sections describe points you should consider when you export particular database objects.

CREATE PUBLIC SYNONYM emp FOR scott.emp;

CONNECT blake/paper; CREATE TRIGGER t_emp BEFORE INSERT ON emp BEGIN NULL; END; CREATE VIEW emp AS SELECT * FROM dual;

Error Handling During an Import Operation

This section describes errors that can occur when you import database objects.

Controlling Index Creation and Maintenance

This section describes the behavior of Import with respect to index creation and maintenance.

Importing Statistics

If statistics are requested at export time and analyzer statistics are available for a table, Export will include the ANALYZE statement used to recalculate the statistics for the table into the dump file. In most circumstances, Export will also write the precalculated optimizer statistics for tables, indexes, and columns to the dump file. See the description of the Export parameter STATISTICS and the Import parameter STATISTICS.

Because of the time it takes to perform an ANALYZE statement, it is usually preferable for Import to use the precalculated optimizer statistics for a table (and its indexes and columns) rather than execute the ANALYZE statement saved by Export. By default, Import will always use the precalculated statistics that are found in the export dump file.

The Export utility flags certain precalculated statistics as questionable. The importer might want to import only unquestionable statistics, not precalculated statistics, in the following situations:

• Character set translations between the dump file and the import client and the import database could potentially change collating sequences that are implicit in the precalculated statistics.

• Row errors occurred while importing the table.

• A partition level import is performed (column statistics will no longer be accurate).

  
  

  Note: Specifying ROWS=n will not prevent the use of precalculated statistics. This feature allows plan generation for queries to be tuned in a nonproduction database using statistics from a production database. In these cases, the import should specify STATISTICS=SAFE.

  
  

In certain situations, the importer might want to always use ANALYZE statements rather than precalculated statistics. For example, the statistics gathered from a fragmented database may not be relevant when the data is imported in a compressed form. In these cases, the importer should specify STATISTICS=RECALCULATE to force the recalculation of statistics.

If you do not want any statistics to be established by Import, you should specify STATISTICS=NONE.

Tuning Considerations for Import Operations

This section discusses some ways to possibly improve the performance of an import operation. The information is categorized as follows:

• Changing System-Level Options

• Changing Initialization Parameters

• Changing Import Options

• Dealing with Large Amounts of LOB Data

• Dealing with Large Amounts of LONG Data

Considerations When Importing Database Objects

The following sections describe restrictions and points you should consider when you import particular database objects.

ANALYZE TABLE [schema.]table VALIDATE REF UPDATE;

UPDATE <tablename> SET <lob column> = EMPTY_BLOB() WHERE <lob column> = IS NULL;  
UPDATE <tablename> SET <lob column> = EMPTY_CLOB() WHERE <lob column> = IS NULL; 

Advantages of Partitioning a Migration

Partitioning a migration has the following advantages:

• Time required for the migration may be reduced, because many of the subjobs can be run in parallel.

• The import can start as soon as the first export subjob completes, rather than waiting for the entire export to complete.

Disadvantages of Partitioning a Migration

Partitioning a migration has the following disadvantages:

• The export and import processes become more complex.

• Support of cross-schema references for certain types of objects may be compromised. For example, if a schema contains a table with a foreign key constraint against a table in a different schema, you may not have the required parent records when you import the table into the dependent schema.

How to Use Export and Import to Partition a Database Migration

To perform a database migration in a partitioned manner, take the following steps:

1. For all top-level metadata in the database, issue the following commands:

   1. exp dba/password FILE=full FULL=y CONSTRAINTS=n TRIGGERS=n ROWS=n INDEXES=n

   2. imp dba/password FILE=full FULL=y

2. For each scheman in the database, issue the following commands:

   1. exp dba/password OWNER=scheman FILE=scheman

   2. imp dba/password FILE=scheman FROMUSER=scheman TOUSER=scheman IGNORE=y

All exports can be done in parallel. When the import of full.dmp completes, all remaining imports can also be done in parallel.

Restrictions When Using Different Releases and Versions of Export and Import

The following restrictions apply when you are using different releases of Export and Import:

• Export dump files can be read only by the Import utility because they are stored in a special binary format.

• Any export dump file can be imported into a later release of the Oracle database.

• The Import utility cannot read export dump files created by the Export utility of a later maintenance release or version. For example, a release 9.2 export dump file cannot be imported by a release 9.0.1 Import utility.

• Whenever a lower version of the Export utility runs with a later version of the Oracle database, categories of database objects that did not exist in the earlier version are excluded from the export.

• Export files generated by Oracle9i Export, either direct path or conventional path, are incompatible with earlier releases of Import and can be imported only with Oracle9i Import. When backward compatibility is an issue, use the earlier release or version of the Export utility against the Oracle9i database.

Examples of Using Different Releases of Export and Import

Table 19-7 shows some examples of which Export and Import releases to use when moving data between different releases of the Oracle database.

Creating Oracle Release 8.0 Export Files from an Oracle9i Database

You do not need to take any special steps to create an Oracle release 8.0 export file from an Oracle9i database. However, the following features are not supported when you use Export release 8.0 on an Oracle9i database:

• Export does not export rows from tables containing objects and LOBs when you have specified a direct path load (DIRECT=y).

• Export does not export dimensions.

• Function-based indexes and domain indexes are not exported.

• Secondary objects (tables, indexes, sequences, and so on, created in support of a domain index) are not exported.

• Views, procedures, functions, packages, type bodies, and types containing references to new Oracle9i features may not compile.

• Objects whose DDL is implemented as a stored procedure rather than SQL are not exported.

• Triggers whose action is a CALL statement are not exported.

• Tables containing logical ROWID columns, primary key refs, or user-defined OID columns are not exported.

• Temporary tables are not exported.

• Index-organized tables (IOTs) revert to an uncompressed state.

• Partitioned IOTs lose their partitioning information.

• Index types and operators are not exported.

• Bitmapped, temporary, and UNDO tablespaces are not exported.

• Java sources, classes, and resources are not exported.

• Varying-width CLOBs, collection enhancements, and LOB-storage clauses for VARRAY columns or nested table enhancements are not exported.

• Fine-grained access control policies are not preserved.

• External tables are not exported.