Performing Customized RMAN TSPITR with an RMAN-Managed Auxiliary Instance

Renaming TSPITR Auxiliary Set Datafiles with SET NEWNAME

To use the SET NEWNAME command to specify a new name for an auxiliary set datafile, enclose your RECOVER TABLESPACE command in a RUN block, and use a SET NEWNAME command within the RUN block to rename the file. For example:

RMAN> RUN
{
  SET NEWNAME FOR DATAFILE '?/oradata/prod/system01.f'
    TO '/disk1/auxdest/system01.f'
  RECOVER TABLESPACE users, tools 
     UNTIL LOGSEQ 1300 THREAD 1
     AUXILIARY DESTINATION '/disk1/auxdest';
}

The resulting behavior depends upon whether there is a file at /disk1/auxdest/system01.f when the RECOVER TABLESPACE command is executed. If there is an image copy backup of the file ?/oradata/system01.f at the specified location, created at an SCN prior to the target time for TSPITR, then the behavior is as described in "SET NEWNAME and CONFIGURE AUXNAME With Auxiliary Set Image Copies". Otherwise, the auxiliary set datafile will be restored to the NEWNAME specified instead of the default location. If your intention is only to control where the auxiliary set datafiles are stored, you should make sure that there is no file stored at the location specified by SET NEWNAME before performing your TSPITR.

Using DB_FILE_NAME_CONVERT to Name Auxiliary Set Datafiles

If you do not want to use an auxiliary destination for all of your auxiliary set datafiles, but you also do not want to name every file individually, you can include a DB_FILE_NAME_CONVERT initialization parameter in the initialization parameter file used by your auxiliary instance. You can only use this method in two circumstances:

• If you are creating your own initialization parameter file for RMAN's automatically managed auxiliary instance, as described in "Customizing Initialization Parameters for the Automatic Auxiliary Instance in TSPITR";

• If you are creating your own auxiliary instance, as described in "Performing RMAN TSPITR Using Your Own Auxiliary Instance".

Refer to the appropriate discussion for your circumstance, to see how to add a parameter to your initialization parameter file.

The DB_FILE_NAME_CONVERT parameter in the auxiliary instance specifies how to derive names for files in the auxiliary instance from the original names of the corresponding files in the target instance.

For example, assume that the target instance contains the following files:

• ?/oradata/trgt/system01.dbf of the SYSTEM tablespace

• ?/oradata/trgt/undotbs01.dbf of the undotbs tablespace

and you need to locate the corresponding files in the auxiliary instance in '/bigtmp', then you would add the following line to the auxiliary instance parameter file:

DB_FILE_NAME_CONVERT=('?/oradata/trgt', '/bigtmp')

The most important thing to remember is that DB_FILE_NAME_CONVERT must be present in the auxiliary instance parameter file.

If the auxiliary instance was manually created, add DB_FILE_NAME_CONVERT to the auxiliary instance parameter file.

Note that you can still rename individual auxiliary set datafiles using SET NEWNAME or CONFIGURE AUXNAME. Also, files that do not match the patterns provided in DB_FILE_NAME_CONVERT will not be renamed. You may wish to use the AUXILIARY DESTINATION parameter of RECOVER TABLESPACE to ensure that all auxiliary set datafiles are sent to some destination. If a file is not renamed at all, TSPITR will fail.

Order of Precedence Among File Renaming Methods in TSPITR

The different methods of renaming files follow an order of precedence, as follows:

• SET NEWNAME

• CONFIGURE AUXNAME

• DB_FILE_NAME_CONVERT

• AUXILIARY DESTINATION argument to RECOVER TABLESPACE

Settings higher on the list override settings lower on the list, in situations where both have been applied (by, for example, running RECOVER TABLESPACE... AUXILIARY DESTINATION on a target database where some auxiliary set datafiles also have auxnames configured with CONFIGURE AUXNAME).

Specifying Auxiliary Instance Control File Location in TSPITR

You can specify your own location for the control file of your auxiliary instance, if you use a client-side initialization parameter file. Set the CONTROL_FILES initialization parameter to specify any location you wish for the control files.

If you do not explicitly specify a location for the control file, RMAN will locate it in the auxiliary destination if you use the AUXILIARY DESTINATION parameter when performing TSPITR. If you do not use an AUXILIARY DESTINATION parameter, the auxiliary instance control files are stored in an operating system-specific location. (on Unix, ORACLE_HOME/rdbms/admin/params_auxinit.ora).

No matter where you store your auxiliary instance control file, it is removed at the end of a successful TSPITR operation. Because control files are relatively small, it is rare that RMAN will encounter a problem creating an auxiliary control file, but if there is not enough space to create the control file, TSPITR will fail.

Specifying Auxiliary Instance Online Log Location in TSPITR

If you specify the LOG_FILE_NAME_CONVERT initialization parameter in your auxiliary instance parameter file, this parameter will determine the online redo log location. Otherwise, if RMAN is using an auxiliary destination and managing the auxiliary instance for you, it creates the online redo log in the auxiliary destination.

Using CONFIGURE AUXNAME With Recovery Set Image Copies in TSPITR

During TSPITR, RMAN looks in the specified AUXNAME location for the datafile, to see whether the file there is an image copy backup of the datafile, with a checkpoint SCN early enough that it can be recovered to the target time for TSPITR. If such an image copy is found, it is used in TSPITR. Otherwise, the datafile is restored and recovered in its original location, and any file in the location specified by the AUXNAME is not changed or deleted.

RMAN> CONFIGURE AUXNAME FOR DATAFILE 'ORACLE_HOME/oradata/trgt/users01.dbf'        TO '/newfs/users1.dbf';
...other RMAN commands, if any...
RMAN> RECOVER TABLESPACE users, tools UNTIL SEQUENCE 1300 THREAD 1;

The primary use of CONFIGURE AUXNAME is as the basis of a technique to make TSPITR faster by eliminating restore times. If you have tablespaces on which you anticipate performing TSPITR, you can include in your backup routine the maintenance of a set of image copies of the affected datafiles, and update these periodically to the earliest point to which you expect to perform TSPITR. The expected usage model is:

• Configure the AUXNAME for the files once, when setting up this strategy

• Perform "BACKUP AS COPY DATAFILE n FORMAT auxname" regularly to maintain the updated image copy, or, for better performance, use an incrementally updated backups strategy as described in Oracle Database Backup and Recovery Basics to keep the image copies up to date without performing full backups of the datafiles

• When TSPITR is needed, specify a target time since the last update of the image copy.

In planning for TSPITR with image copies, remember that you may not know know which tablespaces will require image copies in advance. As discussed in "Determining the Recovery Set: Analyzing Data Relationships", relationships between the tablespaces you wish to TSPITR and other tablespaces may require that you add tablespaces to your final recovery set, and still other tablespaces may wind up in the auxiliary set. You should configure an AUXNAME for each datafile that is likely to be part of your recovery set, and update image copies of all datafiles often.

If you do not correctly anticipate all tablespaces to include in the recovery set, or if for reasons of overhead you do not want to maintain copies of all possible recovery set tablespaces, you can prepare only a subset of the datafiles using this strategy. The TSPITR process is still the same if only a subset of datafiles are prepared. The process takes longer, because RMAN must recover recovery set datafiles for which there are no image copies in their original locations.

Note that the order of precedence of naming methods is still respected when you use CONFIGURE AUXNAME to rename a recovery set file. A SET NEWNAME for a recovery set file set as part of the TSPITR command overrides the effect of the persistent CONFIGURE AUXNAME command for the same file. Behavior in this instance will be as described in "Renaming TSPITR Recovery Set Datafiles with SET NEWNAME". SET NEWNAME used with a recovery set file never refers to an image copy file.

SET NEWNAME and CONFIGURE AUXNAME With Auxiliary Set Image Copies

As with recovery set datafiles, CONFIGURE AUXNAME sets a persistent alternative location for an auxiliary set datafile image copy, and SET NEWNAME sets an alternative location for the duration of a RUN block. However, RMAN handles values for auxiliary set datafiles differently from recovery set datafiles.

If SET NEWNAME is used to specify a new location for an auxiliary set datafile, and there is an image copy at that location with an SCN such that it can be used in TSPITR, then the image copy will be used. If there is no usable image copy at that location, however, RMAN will restore a usable copy from backup. (If an image copy is present but the SCN is after the target time for TSPITR, then the datafile is overwritten by the restored file.)

If CONFIGURE AUXNAME is used to specify a new location for an auxiliary set datafile, and there is an image copy at that location with an SCN such that it can be used in TSPITR, then the image copy will be used. If there is no usable copy at the specified location, the file is restored to this location from bcakup.

As with all auxiliary set files, the file is deleted after successful TSPITR, or left for use in troubleshooting if TSPITR fails, regardless of whether it was an image copy created before TSPITR or restored by RMAN from backup during TSPITR.

Performing TSPITR With CONFIGURE AUXNAME and Image Copies: Scenario

You have enough disk space to save image copies of your entire database for use in TSPITR. In preparation for the possibility that you need perform TSPITR, you perform the following tasks:

• Configure an AUXNAME for each datafile in your database using:

  CONFIGURE AUXNAME FOR DATAFILE n TO auxname_n;
  
  

• Every week on Sunday night you take an image copy of the database which is placed in the files referenced by the configured AUXNAMEs:

  BACKUP AS COPY DATAFILE n FORMAT auxname_n
  
  

  Note that if the image copies are all in the same location on disk and named similarly to the original datafiles, it is possible to use FORMAT or DB_FILE_NAME_CONVERT options of the BACKUP command and use BACKUP AS COPY DATABASE instead of performing individual backups of every datafile. For example if the configured AUXNAMEs are a simple translation of the location 'maindisk' to 'auxdisk', you could use the following backup command:

  BACKUP AS COPY DATABASE DB_FILE_NAME_CONVERT=(maindisk, auxdisk);
  
  

You are then prepared for TSPITR without restoring from backup. If, for example, an erroneous batch job started at November 15 2003, 19:00:00 updates incorrectly the tables in the tablespace parts, you could use the following command to perform TSPITR on tablespace parts:

RECOVER TABLESPACE parts UNTIL TIME 'November 15 2003, 19:00:00';

Because AUXNAMES are configured and refer to datafile copies from an SCN before the TSPITR target time, the auxiliary set and recovery set datafiles are not restored from backup. Instead the datafile copies are directly used in recovery, eliminating the restore overhead.

Note that at the end of the TSPITR, the datafiles for tablespace parts will not be located in the original datafile locations, but in the auxname locations. If only the AUXNAMEs for the auxiliary set should be used (so that the recovery set is left in its original locations), then CONFIGURE AUXNAME ... CLEAR should be used before TSPITR is started. In such a case, though, note that the datafiles will have to be restored.