Veritas Storage Foundation™ 5.0.1 for Oracle RAC Installation, Configuration, and Administrator's Guide Extracts for the HP Serviceguard Storage Management Suite on HP-UX 11i v3

Table 5-1 vxsnap Command for Snapshot Mirror Notes
• 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
Veritas Volume Manager 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.
• Do not place any datafiles, including control files, in the $ORACLE_HOME/dbs directory.
Prerequisites
• Create a separate disk group for Oracle database-related files.
• Do not share volumes between Oracle database files and other software.
• ORACLE_HOME cannot be included in the snapshot mirror.
• 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.
Usage Notes
The example procedure is for existing volumes without existing snapshot plexes or associated
snapshot volumes. In the example procedure, volume_name is the name of either a volume or
a volume set.
To create a snapshot mirror of a volume or volume set
1. 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 in VxVM 4.1, either from the command line
or from within a script, use the vxsnap prepare command as described above.
2. 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.
3. 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.
Preparing Hosts and Storage for Database FlashSnap 55