Creating a snapplan (db2ed_vmchecksnap)
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Creating a snapplan (db2ed_vmchecksnap)

The db2ed_vmchecksnap command creates a snapplan that db2ed_vmsnap uses to create a snapshot of a DB2 database. The snapplan specifies snapshot scenarios (such as online_snapshot, online_mirror, or offline).

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

Table: Parameter values for db2ed_vmchecksnap shows which parameters are set when using db2ed_vmchecksnap to create or validate a snapplan.

Table: Parameter values for db2ed_vmchecksnap

Parameter

Value

SNAPSHOT_VERSION

Specifies the snapshot version for this major release of Veritas Storage Foundation for DB2.

PRIMARY_HOST

The name of the host where the primary database resides.

SECONDARY_HOST

The name of the host where the database will be imported.

PRIMARY_DG

The name of the VxVM disk group used by the primary database.

SNAPSHOT_DG

The name of the disk group containing the snapshot volumes.

The snapshot volumes will be put into this disk group on the primary host and deported. The secondary host can import this disk group to start a clone database.

DB2DATABASE

The name of the DB2 database.

DB2HOME

The home directory of the database.

REDOLOG_DEST

The full path of the redo logs.

SNAPSHOT_MODE

offline or online_snapshot or online_mirror

Specifies whether the database should be offline, online_snapshot, or online_mirror when the snapshot is created. By default, the SNAPSHOT_MODE is online_snapshot.

If the snapshot is created while the SNAPSHOT_MODE for the database is set to online_snapshot or online_mirror, the db2ed_vmsnap command will first put the database into WRITE SUSPEND mode. After db2ed_vmsnap finishes creating the snapshot, it will take the database out of WRITE SUSPEND mode. If the database is offline, it is not necessary to put the database into WRITE SUSPEND mode.

If the SNAPSHOT_MODE is offline, the secondary host must be different than the primary host.

If the SNAPSHOT_MODE is online_mirror, the primary and secondary host must be the same, and the ALLOW_REVERSE_RESYNC parameter must be set to yes in the snapplan. If the SNAPSHOT_MODE is online_snapshot, the clone can be created on either the primary or a secondary host.

SNAPSHOT_PLAN_FOR

The default value is database and cannot be changed.

SNAPSHOT_PLEX_TAG

Specifies the snapshot plex tag. Use this variable to specify a tag for the plexes to be snapshot. The maximum length of the plex_tag is 15 characters.

SNAPSHOT_MIRROR

Specifies the number of mirrors that will be part of the snapshot. The default value is 1.

SNAPSHOT_VOL_PREFIX

Specifies the snapshot volume prefix. Use this variable to specify a prefix for the snapshot volumes split from the primary disk group. A volume name cannot be more than 32 characters. You should consider the length of the volume name when assigning the prefix.

ALLOW_REVERSE_RESYNC

yes or no

By default, reverse resynchronization is off (set equal to no) with the SNAPSHOT_MODE set to online_snapshot. If the SNAPSHOT_MODE is online_mirror, reverse resynchronization is set equal to yes. If ALLOW_REVERSE_RESYNC is set to yes, data from the snapshot volume can be used to overwrite the primary volume.

When you first run db2ed_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.

Before creating a snapplan, make sure the following conditions have been met:

Prerequisites

  • Storage must be configured properly.

    See Hosts and storage for Database FlashSnap .

  • You must be the DB2 instance owner.

  • 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 with LOGRETAIN mode on.

Usage notes

  • The snapplan must be created on the primary host.

  • After creating the snapplan using the db2ed_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 db2ed_vmchecksnap(1M) online manual page for more information.

  • Database FlashSnap commands are not supported for multi-partitioned DB2 databases.

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 db2ed_vmchecksnap command:

    $ /opt/VRTS/bin/db2ed_vmchecksnap -D DB2DATABASE \
-f SNAPPLAN -o setdefaults -t host_name -p PLEX_TAG

  3. Open the snapplan file in a text editor and modify it as needed.

Note:

The default setting for SNAPSHOT_MODE is online_snapshot.

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.

$ cd /export/snap_dir
$ /opt/VRTS/bin/db2ed_vmchecksnap -D PROD -f snap1 -o setdefaults \
-t host1 -p PRODtag
Snapplan snap1 for PROD.
=====================================================
SNAPSHOT_VERSION=5.0
PRIMARY_HOST=host1
SECONDARY_HOST=host1
PRIMARY_DG=PRODdg
SNAPSHOT_DG=SNAP_PRODdg
DB2DATABASE=PROD
DB2HOME=/PROD_HOME
REDOLOG_DEST=/PROD_HOME/inst1/NODE0000/SQL00001/SQLOGDIR/
SNAPSHOT_MODE=online_snapshot
SNAPSHOT_PLAN_FOR=database
SNAPSHOT_PLEX_TAG=PRODtag
SNAPSHOT_MIRROR=1
SNAPSHOT_VOL_PREFIX=SNAP_
ALLOW_REVERSE_RESYNC=no

In this 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.

$ cd /export/snap_dir
$ /opt/VRTS/bin/db2ed_vmchecksnap -D PROD -f snap2 -o setdefaults \
-p PRODtag -t host2
Snapplan snap2 for PROD.
=====================================================
SNAPSHOT_VERSION=5.0
PRIMARY_HOST=host1
SECONDARY_HOST=host2
PRIMARY_DG=PRODdg
SNAPSHOT_DG=SNAP_PRODdg
DB2DATABASE=PROD
DB2HOME=/PROD_HOME
REDOLOG_DEST=/PROD_HOME/inst1/NODE0000/SQL00001/SQLOGDIR/
SNAPSHOT_MODE=online_snapshot
SNAPSHOT_PLAN_FOR=database
SNAPSHOT_PLEX_TAG=PRODtag
SNAPSHOT_MIRROR=1
SNAPSHOT_VOL_PREFIX=SNAP_
ALLOW_REVERSE_RESYNC=no
SNAPSHOT_MIRROR=1
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