Creating multi-mirror snapshots


Creating multi-mirror snapshots
Prev	Creating a snapplan (db2ed_vmchecksnap)	Next

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 with the SNAPSHOT_MIRROR=n keyword in the snapplan.

Note:

Multi-mirror snapshots require no changes to the Command Line usage or arguments for the Flashsnap tools.

Before taking the snapshot, make sure all tagged snapshot mirrors are in the SNAPDONE state.

To create a multi-mirror snaphot

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, db2ed_vmchecksnap fails with appropriate errors.
```
# vxsnap -g dg_a addmir dg_a_vol1 alloc=dg_a03
```
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 db2ed_flashsnap.
```
# vxedit -g dg_a set putil2=db2ed_flashsnap dg_a_vol1-03
```

Add the SNAPSHOT_MIRROR keyword to the snapplan. Here is a sample snapplan.

SNAPSHOT_VERSION=5.0
PRIMARY_HOST=host1
SECONDARY_HOST=host1
PRIMARY_DG=PRODdg
SNAPSHOT_DG=SNAP_PRODdg
DB2DATABASE=PROD
REDOLOG_DEST=/prod_ar
SNAPSHOT_ARCHIVE_LOG=yes
SNAPSHOT_MODE=online
SNAPSHOT_PLAN_FOR=database
SNAPSHOT_PLEX_TAG=db2ed_flashsnap
SNAPSHOT_MIRROR=2
SNAPSHOT_VOL_PREFIX=SNAP_
ALLOW_REVERSE_RESYNC=no