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InfoScale™ 9.0 Storage and Availability Management for DB2 Databases - AIX, Linux

Last Published: 2025-04-13

Product(s): InfoScale & Storage Foundation (9.0)

Platform: AIX,Linux

Section I. Storage Foundation High Availability (SFHA) management solutions for DB2 databases
1. Overview of Storage Foundation for Databases
Section II. Deploying DB2 with InfoScale products
Section III. Configuring Storage Foundation for Database (SFDB) tools
1. Configuring and managing the Storage Foundation for Databases repository database
2. Configuring authentication for Storage Foundation for Databases (SFDB) tools
Section IV. Improving DB2 database performance
Section V. Using point-in-time copies
Section VI. Optimizing storage costs for DB2
1. Understanding storage tiering with SmartTier
  1. About SmartTier
  2. SmartTier in a High Availability (HA) environment
2. SmartTier use cases for DB2
Section VII. Storage Foundation for Databases administrative reference

Creating a snapshot mirror of a volume or volume set used by the database

With Database FlashSnap, you can mirror the volumes used by the database to a separate set of disks, and those mirrors can be used to create a snapshot of the database. These snapshot volumes can be split and placed in a separate disk group. This snapshot disk group can be imported on a separate host, which shares the same storage with the primary host. The snapshot volumes can be resynchronized periodically with the primary volumes to get recent changes of the datafiles. If the primary datafiles become corrupted, you can quickly restore them from the snapshot volumes. Snapshot volumes can be used for a variety of purposes, including backup and recovery, and creating a clone database.

You must create snapshot mirrors for all of the volumes used by the database datafiles before you can create a snapshot of the database. This section describes the procedure used to create snapshot mirrors of volumes.

Use the vxsnap command to create a snapshot mirror or synchronize a snapshot mirror.

Prerequisites

You must be logged in as superuser (root).
The disk group must be version 110 or later.
For more information on disk group versions, see the vxdg(1M) online manual page.
Be sure that a data change object (DCO) and a DCO log volume are associated with the volume for which you are creating the snapshot.
Persistent FastResync must be enabled on the existing database volumes and disks must be assigned for the snapshot volumes.
FastResync optimizes mirror resynchronization by tracking updates to stored data that have been missed by a mirror. When a snapshot mirror is reattached to its primary volumes, only the updates that were missed need to be re-applied to resynchronize it. FastResync increases the efficiency of the volume snapshot mechanism to better support operations such as backup and decision support.
For detailed information about FastResync, see the Storage Foundation Administrator's Guide.
Snapshot mirrors and their associated DCO logs should be on different disks than the original mirror plexes, and should be configured correctly for creating snapshots by the system administrator.
When creating a snapshot mirror, create the snapshot on a separate controller and separate disks from the primary volume.
Allocate separate volumes for archive logs.

Usage Notes

Create a separate disk group for DB2 database-related files.
Do not share volumes between DB2 database files and other software.
Resynchronization speed varies based on the amount of data changed in both the primary and snapshot volumes during the break-off time.
Do not share any disks between the original mirror and the snapshot mirror.
Snapshot mirrors for datafiles and archive logs should be created so that they do not share any disks with the data of the original volumes. If they are not created in this way, the VxVM disk group cannot be split and, as a result, Database FlashSnap will not work.

Note:

Database FlashSnap commands support third-mirror break-off snapshots only. The snapshot mirror must be in the SNAPDONE state.

The following sample procedure is for existing volumes without existing snapshot plexes or associated snapshot volumes. In this procedure, volume_name is the name of either a volume or a volume set.

Note:

You must be logged in as superuser (root) to issue the commands in the following procedure.

To create a snapshot mirror of a volume or volume set

To prepare the volume for being snapshot, use the vxsnap prepare command:
```
# vxsnap -g diskgroup prepare volume \
alloc="storage_attribute ..."
```
The vxsnap prepare command automatically creates a DCO and DCO volumes and associates them with the volume, and enables Persistent FastResync on the volume. Persistent FastResync is also set automatically on any snapshots that are generated from a volume on which this feature is enabled.
For enabling persistent FastResync on a volume either from the command line or from within a script, use the vxsnap prepare command as described above.
To verify that FastResync is enabled on the volume, use the vxprint command:
```
# vxprint -g diskgroup -F%fastresync volume_name
```
This returns on if FastResync is on. Otherwise, it returns off.
To verify that a DCO and DCO log volume are attached to the volume, use the vxprint command:
```
# vxprint -g diskgroup -F%hasdcolog volume_name
```
This returns on if a DCO and DCO log volume are attached to the volume. Otherwise, it returns off.

Create a mirror of a volume:

# vxsnap -g diskgroup addmir volume_name alloc=diskname

Example of creating 3 mirrors for a particular volume:

# vxsnap -g diskgroup addmir datavol \
nmirror=3 alloc=disk1,disk2,disk3

List the available mirrors:

# vxprint -g diskgroup -F%name -e"pl_v_name in \"volume_name\""

Enable database FlashSnap to locate the correct mirror plexes when creating snapshots:
- Set the dbed_flashsnap tag for the data plex you want to use for breaking off the mirror. You can choose any tag name you like, but it needs to match the SNAPSHOT_PLEX_TAG attribute specified in the configuration or snapplan.
```
  # vxedit -g diskgroup set putil2=dbed_flashsnap plex_name
```
- Verify that the dbed_flashsnap tag has been set to the desired data plex:
```
  # vxprint -g diskgroup -F%name -e"pl_v_name in \
  \"volume_name\" && p2 in \"dbed_flashsnap\""
```
If you require a backup of the data in the snapshot, use an appropriate utility or operating system command to copy the contents of the snapshot to tape or to some other backup medium.