RAC Attack - Oracle Cluster Database at Home/Database Backups

We will configure backups to take full advantage of the cluster by running in parallel. Configure the RMAN default channels and parallelism. RMAN> configure device type disk parallelism 2 backup type to compressed backupset; RMAN> configure channel 1 device type disk connect 'sys/racattack@rac1'; RMAN> configure channel 2 device type disk connect 'sys/racattack@rac2'; RMAN> show all;Take a complete hot backup of the entire database. RMAN> backup database plus archivelog; Starting backup at 04-MAY-09 current log archived channel ORA_DISK_1: starting compressed archived log backup set channel ORA_DISK_2: starting compressed archived log backup set ... Finished backup at 04-MAY-09 Starting backup at 04-MAY-09 channel ORA_DISK_1: starting compressed full datafile backup set channel ORA_DISK_2: starting compressed full datafile backup set ... Finished backup at 04-MAY-09 Starting backup at 04-MAY-09 current log archived channel ORA_DISK_1: starting compressed archived log backup set channel ORA_DISK_2: starting compressed archived log backup set ... Finished backup at 04-MAY-09Crosscheck the backup. What happens and why? RMAN> list backupset summary; Key TY LV S Device Type Completion Time #Pieces #Copies Compressed ------- -- -- - ----------- --------------- ------- ------- ---------- 1 B A A DISK 04-MAY-09 1 1 YES 2 B A A DISK 04-MAY-09 1 1 YES 3 B A A DISK 04-MAY-09 1 1 YES 4 B A A DISK 04-MAY-09 1 1 YES 5 B F A DISK 04-MAY-09 1 1 YES 6 B F A DISK 04-MAY-09 1 1 YES 7 B F A DISK 04-MAY-09 1 1 YES 8 B F A DISK 04-MAY-09 1 1 YES 9 B A A DISK 04-MAY-09 1 1 YES 10 B A A DISK 04-MAY-09 1 1 YES RMAN> allocate channel for maintenance device type disk; released channel: ORA_DISK_1 released channel: ORA_DISK_2 allocated channel: ORA_MAINT_DISK_1 channel ORA_MAINT_DISK_1: SID=111 instance=RAC1 device type=DISK RMAN> crosscheck backup; RMAN> list backupset summary; Try this again, without allocating the maintenance channel. What happens and why? Archived Logs Database Recovery