Creating a Snapshot (dbed_vmsnap)

The dbed_vmsnap command creates a snapshot of an Oracle database by splitting the mirror volumes used by the database into a snapshot database. You can use the snapshot image on either the same host as the database or on a secondary host provided storage is shared by the two hosts.

The snapshot image created by dbed_vmsnap is a frozen image of an Oracle database's datafiles. dbed_vmsnap ensures that a backup control file is created when the snapshot database is created, which allows for complete data recovery, if needed.

For a complete list of all snapshot and database statuses, see VERITAS Database FlashSnap Status Information.

Prerequisites

• You must be logged in as the Oracle database administrator.
• You must create and validate a snapplan using dbed_vmchecksnap before you can create a snapshot image with dbed_vmsnap.

Usage Notes

• The dbed_vmsnap command can only be used on the primary host.
• Do not share volumes between Oracle database files and other software.
• When creating a snapshot volume, create the snapshot on a separate controller and on separate disks from the primary volume.
• Make sure your archive log destination is separate from your Oracle database volumes.
• Do not place any datafiles, including control files, in the $ORACLE_HOME/dbs directory.
• Resynchronization speed varies based on the amount of data changed in both the primary and secondary volumes when the mirror is broken off.
• See the dbed_vmsnap(1M) manual page for more information.

  To create a snapshot

1. Change directories to the working directory in which your snapplan is stored:
     $ cd /working_directory
2. If SNAPSHOT_MODE is set to offline in the snapplan, shut down the database.
3. Create the snapshot image using the command:
   $ /opt/VRTS/bin/dbed_vmsnap -S ORACLE_SID -f SNAPPLAN \
   -o snapshot

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     Note    To force snapshot creation, use the -F option. The -F option can be used after a snapshot operation has failed and the problem was fixed without using VERITAS Storage Foundation for Oracle commands. (That is, the volumes were synchronized without using VERITAS Storage Foundation for Oracle commands.) In this situation, the status of the snapplan will appear as unavailable for creating a snapshot. The -F option ignores the unavailable status, checks for the availability of volumes, and creates the snapshot after the volumes pass the availability check.

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     Note    After the snapshot is created, dbed_vmsnap returns values you will need to run dbed_vmclonedb. These values include the snapshot disk group, the snapplan name, and the VxDBA repository volume for a two-host configuration. Make a note of these values so you have them when running dbed_vmclonedb.
   You can also use the command dbed_vmchecksnap -f snapplan -o list to access the information regarding the snapshot disk group, the snapplan name, and the VxDBA repository.

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The snapshot volumes now represent a consistent backup copy of the database. You can backup the database by copying the snapshot volumes to tape or other backup media. For details, see Backing Up the Database from Snapshot Volumes (dbed_vmclonedb). You can also create another Oracle database for decision-support purposes. See Cloning a Database (dbed_vmclonedb) for more information.

For information on creating a snapshot using the GUI, see Using the VERITAS Storage Foundation for Oracle Graphical User Interface.

Example

In this example, a snapshot image of the database, PROD, is created for a single-host configuration. In this case, the SECONDARY_HOST parameter is set the same as the PRIMARY_HOST parameter in the snapplan.

Example

In this example, a snapshot image of the primary database, PROD, is created for a two-host configuration. In this case, the SECONDARY_HOST parameter specifies a different host name than the PRIMARY_HOST parameter in the snapplan.