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The recovery catalog is a repository of information that is used and maintained by Recovery Manager. Recovery Manager uses the information in the recovery catalog to determine how to execute requested backup and restore actions.

The recovery catalog contains informations about the following:

■ datafile and archivelog backup sets and backup pieces ■ datafile copies

■ archived redo logs and copies of them

■ tablespaces and datafiles at the target database

■ named user-created sequences of Recovery Manager and SQL commands

called stored scripts

Operating with a Recovery Catalog

Oracle recommends you use Recovery Manager with a recovery catalog, especially if you have 20 (or more) datafiles. You must frequently resynchronize the recovery catalog with the target database control file to keep it up to date. The more up-to- date the recovery catalog is, the easier it will be to recover. For example, if you have 25 archive logs that have been created subsequent to the last resynchronization, and you experience a failure requiring that you restore the entire database and control file, you must first catalog these files with the recovery catalog before you can use them.

The recovery catalog is maintained solely by Recovery Manager, and the target database never accesses it directly. Recovery Manager propagates information

The Recovery Catalog

about the database structure, archived redo logs, backup sets and datafile copies into the recovery catalog from the target database’s control file.

You do not need an additional database which is solely for the recovery catalog. You can put the recovery catalog in an existing database. It is the database administrator’s responsibility to make the recovery catalog database available to Recovery Manager. Database administrators are also responsible for taking backups of the recovery catalog. Since the recovery catalog resides in an Oracle database, administrators can use Recovery Manager to back it up by reversing the roles of the recovery catalog database and the target database. In other words, the target database can become the recovery catalog database and the recovery catalog database can be treated as a target database.

A single recovery catalog is able to store information for multiple target databases. If the recovery catalog is destroyed and no backups are available, then you can partially reconstruct the catalog from the current control file or control file backups. However, you should always aim to have a valid, recent backup of your recovery catalog.

Propagating Information from the Control File

The size of the target database’s control file will grow, depending on the number of:

■ backups performed ■ archive logs created

■ days (minimum number) this information is stored in the control file

You can specify the minimum number of days this information is kept in the control file using the parameter CONTROL_FILE_RECORD_KEEP_TIME. Entries older than the number of days are candidates for overwrites by newer information. The larger the CONTROL_FILE_RECORD_KEEP_TIME setting is, the larger the control file will be.

At a minimum, you should resynchronize your recovery catalog at intervals less than the CONTROL_FILE_RECORD_KEEP_TIME setting, because after this number of days, the information in the control file will be overwritten with the most recently created information; if you have not resynchronized, and information has been overwritten, this information can not be propagated to the recovery catalog.

Note: The maximum size of the control file is port specific. See your see your operating system-specific Oracle documentation.

See Also:For more information about the

CONTROL_FILE_RECORD_KEEP_TIME parameter, see the Oracle8 Reference.

Operating without a Recovery Catalog

Because most information in the recovery catalog is also available in the target database’s control file, Recovery Manager supports an operational mode where it uses the target database control file instead of a recovery catalog. This operational mode is appropriate for small databases where installation and administration of another database for the sole purpose of maintaining the recovery catalog would be burdensome.

Note that the following features are not supported in this operational mode:

■ tablespace point-in-time recovery ■ stored scripts

■ restore and recovery when the control file is lost or damaged

To restore and recover your database without using a recovery catalog, Oracle recommends that you:

■ Use multiplexed control files (minimum of two), and have each control file on

separate disks to protect against media failure.

Note: You are not required to maintain a recovery catalog with Recovery Manager; however, Oracle recommends that you use one.

The Recovery Catalog

■ Keep excellent record of what files were backed up, the date they were backed

up, and also the names of the backup pieces each file was written to. Keep all Recovery Manager backup logs.

Keeping Information in the Control File

The size of the target database’s control file will grow, depending on the number of:

■ backups performed ■ archive logs created

■ days (minimum) this information is stored in the control file

You can specify the minimum number of days this information is kept in the control file using the parameter CONTROL_FILE_RECORD_KEEP_TIME. Entries older than this number of days are candidates to be overwritten by newer

information. The larger the CONTROL_FILE_RECORD_KEEP_TIME is, the larger the control file will be.

If you do not use a recovery catalog, you may wish to set the

CONTROL_FILE_RECORD_KEEP_TIME parameter to the duration (in days) you intend to keep your backups. This way, the backup information in the control file will not be overwritten before the backups become obsolete.

See Also: For more information about the

CONTROL_FILE_RECORD_KEEP_TIME parameter, see the Oracle8 Reference. WARNING: It is difficult to restore and recover if you lose your control files and do not use a recovery catalog. The only way to restore and recover when you have lost all control files and need to restore and recover datafiles, is to call Oracle WorldWide Support (WWS). WWS will need to know the following:

■ current schema of the database ■ which files were backed up

■ what time the files were backed up

■ names of the backup pieces containing the files

Note: The maximum size of the control file is port specific. See your see your operating system-specific Oracle documentation.