Veritas Storage Foundation 5.0 for Oracle RAC Configuration Guide Extracts for HP Serviceguard Storage Management Suite, Second Edition, May 2008

Using FlashSnap for Backup and Recovery
About Veritas Database FlashSnap
Chapter 5
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Database FlashSnap allows you to check the storage setup against requirements set
forth in the snapplan. Depending on the results, the database administrator may need to
modify the snapplan or the system administrator may need to adjust the storage
configuration. Properly configuring storage is the only aspect of using Database
FlashSnap that requires the system administrator’s participation.
To use Database FlashSnap, a database administrator must first define their snapshot
requirements. For example, they need to determine whether off-host processing is
required and, if it is, which host should be used for it. In addition, it is also important to
consider how much database downtime can be tolerated. Database snapshot
requirements are defined in a file called a snapplan. The snapplan specifies snapshot
options that will be used when creating a snapshot image (such as whether the snapshot
mode will be online, offline, or instant). After creating the snapplan, the database
administrator must validate it to ensure that it is correct. During validation the
snapplan is copied to the repository before using it to create a snapshot. Depending on
the validation results, the database administrator may need to modify the snapplan or
the system administrator may need to adjust the storage configuration.
After storage is configured as specified in the snapplan and the snapplan has been
validated, the database administrator can create snapshots of the database and create
database clones based on the snapshots on either the same host or a secondary one.
A database clone can be used on a secondary host for off-host processing, including
decision-support analysis and reporting, application development and testing, database
backup, and logical error recovery. After a user has finished using the clone on a
secondary host, the database administrator can shut down the clone and move the
snapshot database back to the primary host. Regardless of whether a snapshot is used
on the primary or secondary host, it can be resynchronized with the primary database
using Database FlashSnap. Database FlashSnap utilizes Veritas Volume Manager
FastResync to quickly resynchronize the changed section between the primary and
snapshot.
Database FlashSnap can also be used to recover the primary copy of the database if it
becomes corrupted by overwriting it with the snapshot. You can recover the primary
database with a snapshot using the reverse resynchronization functionality of Database
FlashSnap.
Using Database FlashSnap Commands
The Database FlashSnap feature consists of three commands:
• dbed_vmchecksnap (used on the primary host)
Creates and validates the snapshot plan used to create a snapshot image of an
Oracle database. You can also use dbed_vmchecksnap to copy, list, or remove a
snapplan or make sure the storage is configured properly for the task.
dbed_vmchecksnap is also used on the secondary host to list the snapplan.
• dbed_vmsnap (used on the primary host)
Creates a snapshot image of an Oracle database by splitting the mirror volumes
used by the database. You can also use dbed_vmsnap to resynchronize snapshot
volumes with their original volumes. The command also allows you to resynchronize
the original volumes from the data in the snapshot volumes, which is useful if the
original volumes become corrupted. Resynchronizing the original volumes from the
snapshot volumes is known as reverse resynchronization.