Crosscheck Backup

The RMAN command "crosscheck backup" will verify whether the RMAN backuppieces are still on the tape. If the RMAN backuppieces are no longer available in the tape, then the status will be changed from "A" for available to "X" for expired. Meanwhile, the RMAN command "delete force expired backup" will permanently delete the RMAN backuppieces from the tape that have a status of "X".

I believe "crosscheck backup" only check the MMD (media management device) database. Even the tape that holds the backup piece is not physically on the tape drive, the command will still consider the backup piece is available if it has not been deleted by the "delete obsolete" command (and is within the retention period).

I ran "list backup" and "list backupset", and saw every backup piece from both commands is on the list of backup pieces found Available from "crosscheck backup" command.

What could make the list of obsolete backups and the list of expired backups different?

"delete force expired backup" will permanently delete the RMAN backups that have a status of "X". However, the "force" clause will delete the corresponding records in the RMAN data dictionary even if RMAN cannot find the corresponding RMAN backuppieces on tape. My job running "delete force expired backup" against Veritas NetBackup hanged when the tape was not on the tape drive, but the one without "force" clause worked fine. It seems that "delete expired backup" only deletes entries from the MMD database.

If you just want to see the list of expired backups, use "delete expired backup" and then answer "no" on confirmation, or query the STATUS column (with 'X') of view RC_BACKUP_PIECE.

Sometimes, you may see erros:

RMAN-06207: WARNING: 41 objects could not be deleted for SBT_TAPE channel(s) due
RMAN-06208: to mismatched status. Use CROSSCHECK command to fix status
RMAN-06210: List of Mismatched objects
RMAN-06211: ==========================
RMAN-06212: Object Type Filename/Handle
RMAN-06213: ----- --------------------------------
RMAN-06214: Backup Piece ukjamesq_1_1
RMAN-06214: Backup Piece uljamesr_1_1

The RMAN-06207 and RMAN-06208 errors indicate that the RMAN backuppieces are no longer in the tape. To avoid the two errors, run the following RMAN commands, as shown below.

RMAN> allocate channel for maintenance type 'SBT_TAPE';
RMAN> crosscheck backup;
RMAN> delete expired backup;

But, it seems "crosscheck backup" only looks back to a certain time frame. Fairly old backup pieces may not get the status checked by the command, and the two errors keep showing up in the RMAN log on them. In some occasions, I had to query the BS_KEY column from view RC_BACKUP_PIECE on the catalog database, and then run "RMAN> delete FORCE NOPROMPT BACKUPSET bs_key#;" to delete the backupset after maintenace CHANNEL allocation. Keyword "force" is necessary in below run:

RMAN> delete force NOPROMPT BACKUPSET 218128;
List of Backup Pieces
BP Key BS Key Pc# Cp# Status Device Type Piece Name
------- ------- --- --- ----------- ----------- ----------
218353 218128 1 1 AVAILABLE SBT_TAPE 36j9fc7c_1_1

deleted backup piece
backup piece handle=36j9fc7c_1_1 recid=102 stamp=647475436
Deleted 1 objects

One strange error I got is that I could not use tape channle to run the command on an instance:

RMAN> run {
2> ALLOCATE CHANNEL ch01 TYPE 'SBT_TAPE';
3> crosscheck backup;
4> RELEASE CHANNEL ch01;
5> }

allocated channel: ch01
channel ch01: sid=79 devtype=SBT_TAPE
channel ch01: VERITAS NetBackup for Oracle - Release 6.0 (2006110304)
released channel: ch01
RMAN-00571: ===================================
RMAN-00569: ==== ERROR MESSAGE STACK FOLLOWS ===
RMAN-00571: ===================================
RMAN-03002: failure of crosscheck command at 09/15/2008 12:40:34
RMAN-06091: no channel allocated for maintenance (of an appropriate type)