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

Another key point to consider is that the EqualLogic array automatically creates a snapshot during the

restore operation. The array captures the snapshot and copies the original source volume content into

this snapshot before the actual restore operation. IT storage administrators may find the automatic

creation feature useful since they can analyze the snapshot content to determine the possible root

cause of data corruption failure. This feature is also useful for undoing a snapshot restore operation if

for some reason the restore operation does not succeed.

8.4 Point-in-time recovery using Oracle FLASHBACK DATABASE

The FLASHBACK DATABASE feature uses a different type of log (flashback logs) for keeping track of

database changes. If the flashback feature is enabled, then flashback logs are generated and written

sequentially to flash recovery area during normal database operation.

• While enabling the FLASHBACK DATABASE feature, be sure to plan the flash recovery area so

that it can accommodate growth of these log files. When we executed the 4000 user TPC-C

workload using Quest Benchmark Factory, approximately 30GB of flashback logs were

generated every hour.

• The parameter DB_FLASHBACK_RETENTION_TARGET specifies the maximum amount of time

the database can be rolled back. The flash back recovery area should be able to store all of the

flashback recovery logs that can be generated for the period specified by the

DB_FLASHBACK_RETENTION_TARGET parameter.

8.5 Discovering ORACLE ASM disks on the backup server

ORACLE ASMLIB configured at the OS level on the backup server discovered and listed all of the ASM

disks. However, the Oracle ASM database software installer was not able to recognize any of the same

ASM disks. Even after we installed the ASM software on the backup server, the ASM disks were

discovered at the OS level but the SQL query executed on the ASM instance did not detect any of the

ASM disks. As a result, none of the ASM disk groups were mounted on the backup server. Use the

following steps to fix this issue:

1. When installing Oracle ASM software on the backup server set /dev/oracleasm/disks as the

‘Disk discovery path’.

2. In the file /etc/sysconfig/oracleasm, set “parameter asm_diskstring =

dev/oracleasm/disks/*” if it is not currently set.

8.6 Persistent device mapping on the virtualized backup server

Once you mount the snapshot on the backup server you need to re-discover then login to all targets.

There is no need to create any persistent device mapping for snapshot targets. Do not modify the

/etc/multipath.conf file on the backup server. The ASM labels will be automatically discovered once

the rescan of Oracle ASM disks is complete. Once the snapshots are mounted, the iSCSI targets can be

discovered on the backup server.

8.7 Upgrade Broadcom 57711 driver

There is a documented performance issue with the Broadcom 57711 drivers shipped with ESX 4.1. For

maximum performance, upgrade the Broadcom 57711 firmware and driver to the following version: