How RMAN Creates Files During Duplicate Database

When duplicating a database, RMAN creates the required database files. This section describes the different stages of file creation:

How RMAN Creates the Duplicate Control Files
How RMAN Creates the Duplicate Online Redo Logs
Renaming Datafiles When Duplicating a Database

How RMAN Creates the Duplicate Control Files

The rules of precedence for determining the names for the duplicate database control files are the same used by the SQL statement CREATE CONTROLFILE. When choosing names for the duplicate control files, make sure you set the parameters in the initialization parameter file of the auxiliary database correctly; otherwise, you could overwrite the control files of the target database.

How RMAN Creates the Duplicate Online Redo Logs

One of the principal tasks when duplicating a database is choosing how to name the duplicate database files. Table 13-1 lists the options for creating the names of the online redo logs in the duplicate database. The options appear in the order of precedence.

Table 13-1 Order of Precedence for Online Redo Log Filename Creation

Order	Method	Result
1	Specify the `LOGFILE` clause of `DUPLICATE` command.	Creates online redo logs as specified.
2	Set `LOG_FILE_NAME_CONVERT` initialization parameter.	Transforms target filenames, for example, from `log_` to `duplog_`. Note that you can specify multiple conversion pairs. This parameter allows the redo log to exist as long as the size matches because it uses the `REUSE` parameter when creating the logs.
3	Set one of the Oracle Managed Files initialization parameters.	Transforms target filenames based on the parameters `DB_CREATE_FILE_DEST`, `DB_CREATE_ONLINE_DEST_n`, or `DB_RECOVERY_FILE_DEST`. The rules of precedence are the same used by the SQL statement `ALTER DATABASE ADD LOGFILE`.
4	Do none of the preceding steps.	Makes the duplicate filenames the same as the target filenames. You must specify the `NOFILENAMECHECK` option when using this method and the duplicate database should be in a different host.

The order of precedence determines how RMAN renames the online redo logs. For example, if you specify both the LOGFILE clause and the LOG_FILE_NAME_CONVERT parameter, then RMAN uses the LOGFILE clause. If you specify none of the first three options, then RMAN uses the original target redo log filenames for the duplicate database files.

Caution:

If the target and duplicate databases are in the same host, then do not use the name of an online redo log currently in use by the target database. Also, do not use the name of an online log currently in use by the target database if the duplicate database is in a different host and NOFILENAMECHECK is not used.

Renaming Datafiles When Duplicating a Database

There are several means of specifying new names to be used for the datafiles of your duplicate database. Listed in order of precedence, they are:

Use the RMAN command SET NEWNAME FOR DATAFILE within a RUN block that encloses both the SET NEWNAME commands and the DUPLICATE command.
Use the RMAN command CONFIGURE AUXNAME to specify new names for existing datafiles. Run the CONFIGURE AUXNAME command before the DUPLICATE command.
Specify the DB_FILE_NAME_CONVERT parameter on the DUPLICATE command to specify a rule for converting filenames for any datafiles not renamed with SET NEWNAME or CONFIGURE AUXNAME. Note that you can specify multiple conversion pairs and use ASM disk groups.
Set the DB_FILE_NAME_CONVERT initialization parameter, which is subject to the same semantics and limitations as the DB_FILE_NAME_CONVERT parameter to the DUPLICATE command.
Set the DB_CREATE_FILE_DEST initialization parameter to create Oracle Managed Files datafiles.

If you do not use any of the preceding options, then the duplicate database reuses the original datafile filenames from the target database.

How RMAN Names Temporary Tablespace Datafiles When Duplicating a Database

RMAN re-creates datafiles for temporary tablespaces as part of the process of duplicating a database. There are several means of specifying tempfiles in your duplicate database. Listed in order of precedence, they are:

Use the SET NEWNAME FOR TEMPFILE command within a RUN block that encloses both the SET NEWNAME commands and the DUPLICATE command.
Specify the DB_FILE_NAME_CONVERT parameter to the DUPLICATE command to specify a rule for converting tempfiles not renamed with SET NEWNAME or CONFIGURE AUXNAME. Note that you can specify multiple conversion pairs and use ASM disk groups.
Set the DB_FILE_NAME_CONVERT initialization parameter, which is subject to the same semantics and limitations as the DB_FILE_NAME_CONVERT parameter to the DUPLICATE command.
Set the DB_CREATE_FILE_DEST initialization parameter to create Oracle Managed Files tempfiles.

Preventing Filename Checking when Duplicating a Database

It is possible for CONFIGURE AUXNAME, SET NEWNAME, or DB_FILE_NAME_CONVERT to generate a name that is already in use in the target database. In this case, specify NOFILENAMECHECK on the DUPLICATE command to avoid an error message.

For example, assume that the host A database has two files: datafile 1 is named /oracle/data/file1.f and datafile 2 is named /oracle/data/file2.f. When duplicating to host B, you use a configured channel to duplicate as follows:

RUN
{
  SET NEWNAME FOR DATAFILE 1 TO /oracle/data/file2.f; # rename df 1 as file2.f
  SET NEWNAME FOR DATAFILE 2 TO /oracle/data/file1.f; # rename df 2 as file1.f
  DUPLICATE TARGET DATABASE TO newdb;
}

Even though you issued SET NEWNAME commands for all the datafiles, the DUPLICATE command fails because the duplicate filenames are still in use in the target database. Although datafile 1 in the target is not using /oracle/data/file2.f, and datafile 2 in the target is not using /oracle/data/file1.f, the target filename is used by one of the duplicate datafiles. Thus, you must specify DUPLICATE ... NOFILENAMECHECK to avoid an error.

Skipping Read-Only Tablespaces When Duplicating a Database

When you specify SKIP READONLY, RMAN does not duplicate the datafiles of read-only tablespaces. After duplication is complete, you can query the views in the duplicate database described in Table 13-2 and Table 13-3 to determine which datafiles were skipped. The STATUS and ENABLED columns are the key to determining the current status of the duplicate datafile.

Table 13-2 Read-Only Tablespaces in V$DATAFILE View on Duplicate Database

In the column ...	The value is ...
`STATUS`	`OFFLINE`
`ENABLED`	`READ` `ONLY`
`NAME`	`MISSINGxxx`

Table 13-3 Read-Only Tablespaces in Data Dictionary Views on Duplicate Database

View	In the column ...	The value is ...
`DBA_DATA_FILES`	`STATUS`	`AVAILABLE`
`DBA_TABLESPACES`	`STATUS`	`READ ONLY`

Skipping OFFLINE NORMAL Tablespaces When Duplicating a Database

When tablespaces are taken offline with the OFFLINE NORMAL option before a DUPLICATE operation, RMAN does not duplicate the datafiles of these tablespaces. After duplication, you can manually add or drop these tablespaces. Query the views in the duplicate database described in Table 13-4 and Table 13-5 to determine which datafiles are offline, based on the STATUS and ENABLED columns.

Table 13-4 Offline Tablespaces in V$ Views on Duplicate Database

In the column ...	The value is ...
`STATUS`	`OFFLINE`
`ENABLED`	`DISABLED`
`NAME`	`MISSINGxxx`

Table 13-5 Offline Tablespaces in Data Dictionary Views on Duplicate Database

View	In the column ...	The value is ...
`DBA_DATA_FILES`	`STATUS`	`AVAILABLE`
`DBA_TABLESPACES`	`STATUS`	`OFFLINE`

When you take a tablespace offline with the IMMEDIATE option, RMAN duplicates rather than skips the tablespace because this tablespace requires recovery. As with online tablespaces, RMAN requires a valid backup for duplication.