Wednesday, August 10, 2011
Difference Between OBSOLETE AND EXPIRED Backup
RMAN considers backups of datafiles and control files as obsolete, that is, no longer needed for recovery, according to criteria that we specify in the CONFIGURE command. We can then use the REPORT OBSOLETE command to view obsolete files and DELETE OBSOLETE to delete them .
For ex : we set our retention policy to redundancy 2. this means we always want to keep at least 2 backup, after 2 backup, if we take an another backup oldest one become obsolete because there is 3 backup and we want to keep 2. if our flash recovery area is full then obsolete backups can be overwrite.
A status of "expired" means that the backup piece or backup set is not found in the backup destination or missing .Since backup info is hold in our controlfile and catalog . Our controlfile thinks that there is a backup under a directory with a name but someone delete this file from operating system. We can run crosscheck command to check if these files are exist and if rman found a file is missing then mark that backup record as expired which means is no more exists.