Online mode, third-mirror-break-off type snapshot i.e. online FlashSnap snapshot of a database instance contains all the information needed to create a clone of the database instance. It can act as a template for creating the clone database instances.
You can thus allocate a FlashSnap snapshot that can be used as a master copy for creating one or more clone instances.
The clone instances created from a FlashSnap image, termed as the 'golden image', are incremental copies of the master or the golden image. These depend on the FlashSnap image for their operations.
You can create multiple database instance clones from a single backup image using the staggering technique. Here you create a space-optimized snapshot of a FlashSnap snapshot, and bring up a clone database instance.
Two new configurations parameters are used to support this particular use case.
■ EXTRA_OBJECTS [short form --extra]
■ SOURCE_SNAPSHOT [short form --source]
You need a cache object to create a space-optimized snapshot. This object can either be included in the FlashSnap snapshot, or be created upon snapshot.
EXTRA_OBJECTS is used to specify a cache object to be included in the FlashSnap snapshot. This parameter is not needed if you create a cache object after the creation of a FlashSnap snapshot.
173 Administering space-optimized snapshots Creating multiple clones using FlashSnap snapshots
To create database clones using space-optimized snapshots from a FlashSnap golden image
174 Administering space-optimized snapshots Creating multiple clones using FlashSnap snapshots
1 Create an online FlashSnap snapshot (golden image) to be used as the source snapshot.
$ vxsfadm -s flashsnap -a oracle --name friday -o snapshot \ --oracle_sid sfaedb --oracle_home /ora_base/db_home \
--extra_objects datadg:cacheobj --extra_objects datadg2:cacheobj2 Validating database configuration for third-mirror-break-off snapshot:
ORACLE_SID = sfaedb
snapshot started at Mon Jan 30 15:05:15 2012.
Putting database in backup mode ... Done
Validating database volume layout for third-mirror-break-off snapshot:
Data volumes ready for snapshot:
Volume/volume-set datavol2 of diskgroup datadg2 mounted on /data2.
Storage units to be used for snapshot from diskgroup datadg2:
disk_6 Volume/volume-set datavol of diskgroup datadg mounted on /data.
Storage units to be used for snapshot from diskgroup datadg:
disk_3
Archivelog volume ready for snapshot:
Volume/volume-set archvol of diskgroup datadg mounted on /arch.
Storage units to be used for snapshot from diskgroup datadg:
disk_4
SNAPSHOT_VOL_PREFIX = SNAP_
SNAPSHOT_DG_PREFIX = SNAP_
Database volume layout validated successfully.
Creating snapshot volumes for data volumes ... Done
Taking database out of backup mode ... Done
Flushing online redo logs ... Done
Creating snapshot volume for archivelog volume ... Done Copying snapshot information to snapshot volume ... Done
Creating snapshot diskgroups ... Done
Deporting snapshot diskgroups ... Done
SNAP_datadg2 SNAP_datadg
snaphot ended at Mon Jan 30 15:05:28 2012.
You can use the--extra_objectsoption to include cache objects from the original disk group in the snapshot disk groups. In the example procedure, cache objects cacheobj and cacheobj2 from datadg and datadg2 disk groups are included in the snapshot disk groups SNAP_datadg and SNAP_datadg2.
175 Administering space-optimized snapshots Creating multiple clones using FlashSnap snapshots
If you do not use this option, you must manually create cache objects in the snapshot disk groups.
176 Administering space-optimized snapshots Creating multiple clones using FlashSnap snapshots
See“FlashSnap configuration parameters”on page 286.
177 Administering space-optimized snapshots Creating multiple clones using FlashSnap snapshots
2 Create clones using space-optimized snapshots.
$ vxsfadm -s sos -a oracle --name reporting --source-snapshot \ friday --prefix RPT -o clone -r primary-host
Validating database configuration for space-optimized snapshot:
ORACLE_SID = sfaedb
Validating source snapshot friday ... Done
Validating database volume layout for space-optimized snapshot:
CACHE_OBJECT = SNAP_datadg2:cacheobj2,SNAP_datadg:cacheobj SNAPSHOT_VOL_PREFIX = RPT
Database volume layout validated successfully.
Creating snapshot volumes for data volumes ... Done Generated mount path: /var/tmp/IKrlBXRcZ_
Mounting snapshot volumes ... Done
Cloning using autogenerated SID ( sfaxwYXY )
Preparing parameter file for clone database ... Done
Mounting clone database ... Done
Starting database recovery ...
Clone database sfaxwYXY is open.
This command creates a clone database using the FlashSnap snapshot friday as the golden image. You can create multiple space-optimized snapshots using the same golden image.
The golden image snapshot, like any other FlashSnap snapshot, can be imported on a host sharing storage with the host running production database.
You can create database clones using space-optimized snapshots from a FlashSnap golden image in such off-host scenarios as well. Note that you must usevxsfadm -roption in such cases.
You can create the clones on a host different from the host on which the production database is running. In this scenario, you must specify the primary host using the-roption ofvxsfadm. When the clone is no longer required, you can delete it by using the-o deleteoption ofvxsfadm.
Note: You cannot resynchronize the FlashSnap snapshot while there exist space-optimized snapshots created by using that FlashSnap snapshot as a golden image.
178 Administering space-optimized snapshots Creating multiple clones using FlashSnap snapshots
See“vxsfadm command reference”on page 282.
See“Space-optimized snapshots configuration parameters”on page 290.
See“Space-optimized snapshots supported operations”on page 292.
Recovering the clone database manually
For Oracle databases, you can perform some special operations such as recovering the database to a System Change Number (SCN) or a particular time. You can use the mountdb operation to perform the database recovery. This operation can be performed after completing the mount or the snap operations.
To recover the database manually
1 Mount the database without recovering or applying the logs.
$ /opt/VRTSdbed/bin/vxsfadm -s sos -a oracle \
-o mountdb --oracle_sid sfaedb --oracle_home /ora_base/db_home \ --sos_name TEST1
Mounting snapshot volumes ... Done
If you execute this command after the snap operation, it mounts the file systems and the clone database. Please note that archive logs are not applied and the database is not open for read write operations. You can recover the database by using basic Oracle recovery commands.
See“Manual recovery of a clone database”on page 322.
See“Manual recovery after a restore operation”on page 323.
2 Update the repository to change the database state toclone.
$ /opt/VRTSdbed/bin/vxsfadm -s sos -a oracle \ -o update_status --oracle_sid sfaedb \
--oracle_home /ora_base/db_home --sos_name TEST1
This step is for bookkeeping that needs to be performed to update the state of the space-optimized snapshots service in repository to clone state after manual recovery.
179 Administering space-optimized snapshots Recovering the clone database manually