Creating a Snapplan (dbed_vmchecksnap)

The dbed_vmchecksnap command creates a snapplan that dbed_vmsnap uses to create a snapshot of an Oracle database. The snapplan specifies snapshot scenarios (such as online, offline, or instant).

You can name a snapplan file whatever you choose. Each entry in the snapplan file is a line in parameter=argument format.

When using dbed_vmchecksnap to create or validate a snapplan, the following parameters are set:

When you first run dbed_vmchecksnap, use the -o setdefaults option to create a snapplan using default values for variables. You may then edit the file manually to set the variables for different snapshot scenarios.

Prerequisites

• Storage must be configured as specified in Preparing Hosts and Storage for Database FlashSnap.
• You must be the Oracle database administrator.
• The disk group must be version 110 or later. For more information on disk group versions, see the vxdg(1M) manual page.
• Be sure that a DCO and DCO volume are associated with the volume for which you are creating the snapshot.
• Snapshot plexes and their associated DCO logs should be on different disks than the original plexes, and should be configured correctly for creating snapshots by the system administrator.
• Persistent FastResync must be enabled on the existing database volumes and disks must be assigned for the snapshot volumes.
• The database must be running in archive log mode. Archive log mode is set in the Oracle initialization parameter file (init.ora).
• The Oracle database must have at least one mandatory archive destination. For further details, see Establishing a Mandatory Archive Destination.
• ORACLE_HOME cannot reside on disk which will be used for snapshot.

Usage Notes

• The snapplan must be created on the primary host.
• After creating the snapplan using the dbed_vmchecksnap command, you can use a text editor to review and update the file, if necessary.
• It is recommended that you create a local working directory to store your snapplans in.
• See the dbed_vmchecksnap(1M) online manual page for more information.
• If the SNAPSHOT_MODE for the database is set to online, the primary and secondary hosts can be the same. If the SNAPSHOT_MODE is set to offline or instant, the primary and secondary hosts must be different.

  To create a snapplan

1. Change directories to the working directory you want to store your snapplan in.
   $ cd /working_directory
2. Create a snapplan with default values using the dbed_vmchecksnap command:
   $ /opt/VRTS/bin/dbed_vmchecksnap -S ORACLE_SID \
   -H ORACLE_HOME -f SNAPPLAN -o setdefaults -t host_name \
   [-p PLEX_TAG]
3. Open the snapplan file in a text editor and modify it as needed.

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

Example

In this example, a snapplan, snap1, is created for a snapshot image in a single-host configuration and default values are set. The host is named host1 and the working directory is /export/snap_dir.

Example

In the following example, a snapplan, snap2, is created for a snapshot image in a two-host configuration, and default values are set. The primary host is host1, the secondary host is host2, and the working directory is /export/snap_dir.

By default, a snapplan's SNAPSHOT_PLEX_TAG value is set as dbed_flashsnap. You can use the -p option to assign a different tag name. Make use of the -p option when creating the snapplan with the setdefaults option.

Example

In the following example, the -p option is used with setdefaults to assign my_tag as the SNAPSHOT_PLEX_TAG value.

Creating Multi-mirror Snapshots

To make Database Snapshots highly available, the snapped snapshot volume should contain more than one mirror. This makes the snapshot volumes available even if one of the mirrors gets disabled. Snapshot volumes can be mounted and the entire database snapshot is usable even if one of the mirror gets disabled. The multi-mirror snapshots are enabled via SNAPSHOT_MIRROR=<n> in the snapplan.

The following sample explains the setup and the procedure for taking multi-mirror snapshots:

1. Add the second mirror and DCO log. When allocating storage for the second mirror and DCO logs, make sure the snap volumes are splittable. If snap volumes are not splittable, dbed_vmchecksnap fails with appropriate errors.

   Tag the newly added mirror with the same tag as that of the first mirror.

   Assume that the volume has fastresync = on, has dcolog = on, and already has one SNAPDONE mirror and is tagged with dbed_flashsnap.

   
     # vxsnap -g dg_a  addmir dg_a_vol1 alloc=dg_a03
     # vxedit -g dg_a set putil2=dbed_flashsnap dg_a_vol1-03
2. Add keyword to the snapplan.Here is a sample snapplan.
     SNAPSHOT_VERSION=4.0
     PRIMARY_HOST=host1
     SECONDARY_HOST=host1
     PRIMARY_DG=PRODdg
     SNAPSHOT_DG=SNAP_PRODdg
     ORACLE_SID=PROD
     ARCHIVELOG_DEST=/prod_ar
     SNAPSHOT_ARCHIVE_LOG=yes
     SNAPSHOT_MODE=online
     SNAPSHOT_PLAN_FOR=database
     SNAPSHOT_PLEX_TAG=dbed_flashsnap
     SNAPSHOT_VOL_PREFIX=SNAP_
     ALLOW_REVERSE_RESYNC=no
     SNAPSHOT_MIRROR=2

Establishing a Mandatory Archive Destination

When cloning a database using Database FlashSnap (see Cloning a Database (dbed_vmclonedb) for details), the Oracle database must have at least one mandatory archive destination, otherwise dbed_vmchecksnap results in this error message:

This example shows how to establish a mandatory archive destination using SQL*Plus:

For more information about Oracle parameters for archiving redo logs, see your Oracle documentation.