Backing Up the Database from Snapshot Volumes (dbed_vmclonedb)

Snapshots are most commonly used as a source for backing up a database. The advantage of using snapshot volumes is that the backup will not contest the I/O bandwidth of the physical devices. Making the snapshot volumes available on a secondary host will eliminate the extra loads put on processors and I/O adapters by the backup process on the primary host.

A clone database can also serve as a valid backup of the primary database. You can back up the primary database to tape using snapshot volumes.

The figure below, Example System Configuration for Database Backup on the Primary Host shows a typical configuration when snapshot volumes are located on the primary host.

Example System Configuration for Database Backup on the Primary Host

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The following figure, Example System Configuration for Database Backup on a Secondary Hostshows a typical configuration when snapshot volumes are used on a secondary host.

Example System Configuration for Database Backup on a Secondary Host

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Prerequisites

• You must be logged in as the Oracle database administrator to use dbed_vmclonedb command.
• Before you can use the dbed_vmclonedb command, you must complete the steps in Summary of Database Snapshot Steps, Validating a Snapplan (dbed_vmchecksnap), and Creating a Snapshot (dbed_vmsnap).
• The volume snapshot must contain the entire database.
• Before you can use the dbed_vmclonedb command with the -r relocate_path option (which specifies the initial mount point for the snapshot image), the system administrator must create the mount point and then change the owner to the Oracle database administrator.

Usage Notes

• The dbed_vmclonedb command can be used on the secondary host.
• In a single-host configuration, the primary and secondary hosts are the same.
• In a single-host configuration, -r relocate_path is required.
• In a two-host configuration, the vxdbavol=vol_name option is required.
• If SNAPSHOT_MODE is set to offline or instant, a two-host configuration is required and -r relocate_path is not allowed.
• See the dbed_vmclonedb(1M) manual page for more information.

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  Note    You cannot access Database FlashSnap commands (dbed_vmchecksnap, dbed_vmsnap, and dbed_vmclonedb) with the VxDBA menu utility.

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Mounting the Snapshot Volumes and Backing Up

Before using the snapshot volumes to do a backup, you must first mount them as follows.

  To mount the snapshot volumes

Use the dbed_vmclonedb command as follows:

You can now backup an individual file or a group of files under a directory onto the backup media.

Example

In this example, snapshot volumes are mounted.

  To mount a Storage Checkpoint carried over from the snapshot volumes to a secondary host

1. On the secondary host, list the Storage Checkpoints carried over from the primary database using:
   $ /opt/VRTS/bin/dbed_ckptdisplay -S ORACLE_SID -n
2. You can mount one of the listed Storage Checkpoints using:
   $ /opt/VRTS/bin/dbed_ckptmount -S ORACLE_SID -c CKPT_NAME \
   -m MOUNT_POINT

Limitations

• Any mounted Storage Checkpoints must be unmounted before running the following commands:

$ /opt/VRTS/bin/dbed_vmclonedb -o umount,new_sid=new_sid \
-f SNAPPLAN
• It is only possible to mount a Storage Checkpoint carried over with the snapshot volumes in a two-host configuration if the snapshot volumes were mounted with the dbed_vmclonedb command with the -o mount option without the use of -r relocate_path.
• Storage Checkpoints carried over with the snapshot volumes can be mounted before a clone database is created using dbed_vmclonedb with the -o mount option. After a clone database is created using dbed_vmclonedb with the -o recoverdb option, however, Storage Checkpoints are no longer present.

  To backup the database using the snapshot

Copy the snapshot volumes to tape or other appropriate backup media.

Restoring from Backup

Backup copies are used to restore volumes lost due to disk failure, or data destroyed due to human error. If a volume's data is corrupted and you know that you need to restore it from backup, you can use Database FlashSnap's reverse resynchronization function to restore the database. See Resynchronizing Your Database to the Snapshot for more information.