Oracle 10g Top 5 Timed Events - backup timed events

In the TOP 5 Times Events, i have highlighted couple of events related to backup job. IMM OP wait event falls under the other category but related to the RMAN backup. The other one you see is Backup : sbtbackup falls under the administrative category also realted to the RMAN. These wait events will occur when there is RMAN backup running on the server.

imm op

Meaning: Waiting for an IMMEDIATE I/O request to a slave process to end.The event "imm op" may occur if I/O slaves are used,

that is, if parameters such as DBWR_IO_SLAVES or BACKUP_TAPE_IO_SLAVES are used.

BACKUP_TAPE_IO_SLAVES is set to TRUE in the case of a RMAN backup if dedicated I/O slave processes are to copy backup write

processes to tape and not the Oracle shadow processes. In this case, "imm op" waits only affect the backup runtime, but not the live system.

Backup: sbtbackup

Meaning: Wait situations during RMAN backup. The wait events that begin with "Backup: sbt" are associated with wait situations during a RMAN backup. This means they only affect the backup runtime.

One has to be careful with these events especially during the peak time, they should not be in the TOP 5. If they are found in the peak time, one has to look at scheduling the backup during the non peak time and also these will occur when RMAN is backing up the database directly to the TAPE instead to a disk. As backup is a heavy DISK and CPU intensive job, it has to be done during the non peak time only.