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Best Practices for Oracle 11g Backup and Recovery using RMAN and Dell EqualLogic Snapshots

You can see in Figure 4 that a significant incremental increase in CPU utilization occurred at the start

of RMAN backup processing. We also measured a significant impact on the performance of the

production database (increase in response time and decrease in TPS shown in the bottom part of

Figure 4). The impact on the production database is due to how RMAN quiesces database I/O activity

at the beginning of the process. Measureable impact on database performance was limited to the first

two minutes of the backup process, while the CPU impact remained during the entire duration of

RMAN backup processing.

4.1.3 Database complete recovery time: RMAN full backup

The database recovery operation after an RMAN full backup involves restoring the database to the

previous full backup point, then applying all redo logs necessary to reach the recovery point objective.

The time to complete database recovery depends primarily on:

• The age of the previous full backup.

• The volume of transactions recorded in the redo logs.

We continued to run the 4000 user TPC-C workload on the 200GB production database for 6 hours

after completing an initial RMAN full backup. After six hours we completed an RMAN restore and

recovery process. The redo logs generated after the previous backup were used for database recovery.

We measured the following restore and recovery times:

• Time to restore the database: 45 minutes

• Time to recover the database using redo logs: 106 minutes

• Total recovery time: 151 minutes

4.2 RMAN incremental backup and recovery

During this test we executed the same backup and recovery scenarios using RMAN incremental

backups instead of a full backup. We ran the following test sequence:

• Created incremental backups (level 0 + level 1) while running the TPC-C database workload

• Database recovery from incremental backup

4.2.1 Database backup time: RMAN incremental

The level 1 backup was initiated after running the TPC-C transactions for 2.5 hours past completion of

the level 0 backup. The time necessary to create the level 0 and level 1 backups of our test database

(while under TPC-C transactional load) are shown below.

RMAN Incremental backup Duration

(Minutes)

Size (GB)

Time to create Level 0 backup 56 150

Time to create Level 1 backup 50 50