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10g RMAN Benefits of Simplified Recovery Through Resetlogs. (Doc ID 472536.1)

Last updated on DECEMBER 05, 2018

Applies to:

Oracle Database - Enterprise Edition - Version and later
Information in this document applies to any platform.
***Checked for relevance on 14-Aug-2013***


10g RMAN Benefits of Simplified Recovery Through Resetlogs

After you perform an incomplete (Point-in-time) recovery, you need to open the database with the RESETLOGS option:

SQL> alter database open resetlogs;

The RESETLOGS operation creates a new incarnation of the database and resets the logs. Prior to Oracle 10g, the newly generated redo log files could not be used with the backups taken in the past. Therefore, it was important to take an immediate backup, since all previous backups became invalid. In addition, if you used the RMAN catalog for future backups, you needed to issue the following command to make the RMAN catalog aware of the new incarnation of the database.

RMAN> reset database;

In Oracle 10g, you no longer have to back up your database following an incomplete recovery and OPEN RESETLOGS operations.

This new feature is also applicable for performing a recovery using a backup control file and opening the database with the RESETLOGS operation.

The Simplified Recovery Through Resetlogs feature provides the following benefits:

* There is no need to perform a full backup after an incomplete recovery.
* There is no need to recreate a new standby database after a failover operation.
* There is no need to change any backup scripts, as there are no changes in the recovery commands to take advantage of this functionality.
* You can take incremental backups based on full backups of a previous incarnation when you use RMAN.
* Block media recovery can restore backups from parent incarnation backups and recover the corrupted blocks through a RESETLOGS operation.

You can use the newly generated logs with an earlier incarnation of the database. Oracle 10g introduces a new format specification for archived log files. This new format avoids overwriting archived redo log files with the same sequence number across incarnations.

SQL> show parameter log_archive_format
----------------------- ----------- ----------------
log_archive_format string %t_%s_%r.dbf

The format specification is %r and represents the resetlogs id. It is included in the default format for the log_archive_format initialization parameter. It will ensure that a unique name is constructed for the archived redo log file during RMAN restore and SQL*plus auto recovery mode.

The database would not start if you remove the %r from the log archive format specification:

SQL> startup
ORA-19905: log_archive_format must contain %s, %t and %r <<


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