What is a control file autobackup?

What is a control file autobackup?

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A control file autobackup is a backup of the control file and the server parameter file (if used), which Recovery Manager (RMAN) automatically takes whenever the database structure metadata in the control file changes or whenever a backup or copy operation is performed using RMAN.

The autobackup feature can be enabled by executing the CONFIGURE CONTROLFILE AUTOBACKUP ON; command at the RMAN prompt. If the autobackup feature is enabled, RMAN automatically backs up the current control file and the current server parameter file (SPFILE) in the following circumstances:

After every BACKUP or COPY command executed at the RMAN prompt.

After every BACKUP or COPY command within a RUN block, which is not followed by another BACKUP or COPY command.

At the end of every RUN block if the last command in the block was either a BACKUP or a COPY command.

After structural changes made in the database. For example, after adding a new tablespace, altering the state of a tablespace or data file, renaming a file, adding a new online redo log, adding a new redo thread, etc.

A control file autobackup enables RMAN to recover a database even if the current control file, recovery catalog, and server parameter file are inaccessible. As the autobackup is stored in a well-known format (i.e., it has a default name), RMAN can search for the autobackup without accessing the RMAN repository (the recovery catalog or the control file's header), and then it can restore the server parameter file from the autobackup. Once the Oracle instance is started using the restored server parameter file, RMAN can restore the control file from the autobackup. Once the control file is restored, the database can be mounted, and the data files can be restored using the RMAN repository in the control file's header.

The autobackup feature can be disabled by executing the CONFIGURE CONTROLFILE AUTOBACKUP OFF; command at the RMAN prompt. By default, the autobackup feature is disabled.

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