LEAST amount of recovery that has to be done before a database restored

Q? What is the LEAST amount of recovery that has to be done before a database restored from a hot rman backup can be opened?


A: ALL archivelogs from backup start to backup end must be applied before the database can be opened - this is the MINIMUM amount of recovery needed.

To determine which log was current at the time the backup completed, note the COMPLETION time of the rman database backup - take this from the backup log.

If the backup log is not longer available query the rman metadata but make sure you set NLS_DATE_FORMAT before invoking rman so that timestamps as well as date are returned:


- for unix:     %export NLS_DATE_FORMAT='dd-mon-rr hh24:mi:ss'

                %rman target /


- for windows:  >set nls_date_format=dd-mon-rr:hh24:mi:ss

                >rman target /


To find your backup:

RMAN>LIST BACKUP OF DATABASE COMPLETED AFTER '<date>';

or

RMAN>LIST BACKUP OF DATABASE COMPLETED AFTER 'sysdate -n';


Set <date> to limit the output to the backups that you are interested and note the completion time - for a multi-piece backup, note the completion time of the LAST backuppiece created.

Lets say, the backup completed 04-Jun-11 13:13:05 query the controlfile:


SQL>ALTER SESSION SET NLS_DATE_FORMAT='DD-MON-RR HH24:MI:SS';

SQL> SELECT THREAD#, SEQUENCE#, FIRST_TIME, NEXT_TIME FROM V$ARCHIVED_LOG WHERE '04-JUN-11 13:13:05' BETWEEN FIRST_TIME AND NEXT_TIME;


If the above query does not return any rows, it may be that the information has aged out of the controlfile - run the same query against v$log_history.

The sequence# returned by the above query is the log sequence current at the time the backup ended - let say 530 thread 1.  For minimum recovery use:


RMAN>RUN { SET UNTIL SEQUENCE 531 THREAD 1;

RESTORE DATABASE;

RECOVER DATABASE;

ALTER DATABASE OPEN RESETLOGS;

}


If this is a RAC implementation the use this SQL instead to query the controlfile:

SQL>SELECT THREAD#, SEQUENCE#, FIRST_CHANGE#, NEXT_CHANGE# FROM V$ARCHIVED_LOG WHERE '04-JUN-11 13:13:05' BETWEEN FIRST_TIME AND NEXT_TIME;


For minimum recovery use the log sequence and thread that has the lowest NEXT_CHANGE# returned by the above query.


Reference : How to determine minimum end point for recovery of an RMAN backup (Doc ID 1329415.1)

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