Managing the Control File When You Use a Recovery Catalog

Your goal is to ensure that the metadata in the recovery catalog is current. Because the recovery catalog obtains its metadata from the target control file, the currency of the data in the catalog depends on the currency of the data in the control file. You need to make sure that the backup metadata in the control file is recorded in the catalog before it is overwritten with new records.

The CONTROL_FILE_RECORD_KEEP_TIME initialization parameter determines the minimum number of days that records are retained in the control file before they are candidates for being overwritten. Hence, you must ensure that you resynchronize the recovery catalog with the control file records before these records are erased. As described in "Resynchronizing the Recovery Catalog and CONTROL_FILE_RECORD_KEEP_TIME", you should perform either of the following actions at intervals less than the CONTROL_FILE_RECORD_KEEP_TIME setting:

• Make a backup, thereby performing an implicit resynchronization of the recovery catalog

• Manually resynchronize the recovery catalog with the RESYNC CATALOG command

So, to ensure the currency of the information in the recovery catalog, the frequency of resynchronizations should be related to the value for the CONTROL_FILE_RECORD_KEEP_TIME initialization parameter.

One problem can arise if the control file becomes too large. The size of the target database control file grows depending on the number of:

• Backups that you perform

• Archived redo logs that the database generates

• Days that this information is stored in the control file

As explained in Oracle Database Backup and Recovery Basics, if the control file grows so large that it can no longer expand because it has reached either the maximum number of blocks or the maximum number of records, then the database may overwrite the oldest records even if their age is less than the CONTROL_FILE_RECORD_KEEP_TIME setting. In this case, the database writes a message to the alert log. If you discover that this situation occurs frequently, then reducing the value of CONTROL_FILE_RECORD_KEEP_TIME and increase the frequency of resynchronizations.