Using Instant Snapshots

Intelligent storage devices are available that can provide almost instantaneous copies of data sets at a specified point in time by controlling the placement of data on large arrays of disks.

Restoration of such copies is also nearly instantaneous, which can significantly reduce recovery time. BMC AMI Recover can use such copies, made by the BMC AMI Copy utility with the BMC EXTENDED BUFFER MANAGER (XBM) or SNAPSHOT UPGRADE FEATURE (SUF) products, for the forward recovery of table spaces and indexes.

Registration of Instant Snapshots

LP Instant Snapshots are registered as IBM FlashCopy (FC) copies in SYSIBM.SYSCOPY. Other Instant Snapshots are registered in the BMC BMCXCOPY table with an STYPE of V. They are not registered in SYSIBM.SYSCOPY because the IBM Db2 COPY utility does not recognize them. Standard Db2 utilities can only use FlashCopy (FC) copies registered in SYSIBM.SYSCOPY.

If a backup copy (LB or RB) is produced and its associated primary copy (LP or RP) is an Instant Snapshot, the backup is registered in BMCXCOPY, even if it is a standard copy.

SNAP phase for Instant Snapshot recovery

The SNAP phase is used to restore table spaces and indexes by using Instant Snapshots. The SNAP phase interfaces with XBM. The SNAP phase is followed by a MERGE phase if required (if there are logs to apply, if output copies are requested, or if keys are extracted).

For multi-data-set, nonpartitioned spaces where a DSNUM ALL recovery is requested, a single SNAP phase restores all Instant Snapshots, followed by a MERGE phase.

INCOPY FULL SNAPSHOT

The INCOPY FULL specification includes a SNAPSHOT option so that you can use a non-registered Instant Snapshot as an input copy.

Executing an Instant Snapshot recovery

To use Instant Snapshots in recovery, you must specify the XBMID installation option or XBMID on the OPTIONS command.

XBMID names the subsystem from which the requested Instant Snapshots had been made.

The following sample syntax provides an example of the syntax needed for a recovery that uses an Instant Snapshot:

OPTIONS XBMID DBXM
RECOVER TABLESPACE PAYROLL.EMPLOYEE
        TABLESPACE PAYROLL.TAXRATES
        TABLESPACE PAYROLL.BENEFITS
        INDEXSPACE PAYROLL.EMPNUMIN
        INDEXSPACE PAYROLL.EMPNAMIN
        INDEXSPACE PAYROLL.TAXSTSIN
        INDEXSPACE PAYROLL.BENEPLIN

Instant Snapshots and migration

When you use Instant Snapshots for migration and specify the OBIDXLAT option or when you specify the IMPORT or MIGRATE command, BMC AMI Recover automatically detects if the OBIDs have not changed and avoids the overhead of reading and writing all of the pages.

Instant Snapshot restrictions

The following restrictions apply to recoveries that use Instant Snapshots:

Instant Snapshot copies cannot be created with the OUTCOPY YES or OUTCOPY ONLY options.
When Instant Snapshots are made with BMC AMI Copy for use with BMC AMI Recover for a nonpartitioned, multi-data-set space, GROUP YES is required and all of the copies must be Instant Snapshots if RECOVER DSNUM ALL is specified for the space. For a DSNUM n recovery, these restrictions do not apply.
If an Instant Snapshot copy is used to recover the object, REDEFINE YES has no effect and the data sets are processed as if REDEFINE NO had been specified.

XBM diagnostics

You can use EXTENDED BUFFER MANAGER (XBM) to diagnose problems with and improve the performance of Instant Snapshots. To print the XBM diagnostics in the BMC AMI Recover output, include an AFRDBG DD in the BMC AMI Recovery JCL.

//AFRDBG DD DUMMY

Instant Snapshot use by other BMC utilities

Instant snapshots are recognized and used by other BMC products that access the BMCXCOPY table in which these copies are registered.

BMC AMI Copy for Db2 produces these copies for recovery.
BMC AMI Recovery Manager for Db2 reports these copies and recognizes them for recovery when generating and optimizing the necessary JCL.
The BMC AMI Copy MODIFY command deletes the Instant Snapshots from BMCXCOPY and the ICF catalog through its standard functions. All commands operate on the Instant Snapshots registered in BMCXCOPY and their associated standard backup copies. However, template-generated copies are standard copies only, not Instant Snapshot copies.
UNLOAD PLUS for DB2 unloads data from these copies.

IBM FlashCopy

BMC AMI Recover can use IBM FlashCopy image copies as a recovery resource.

The FlashCopy image copies are handled in much the same way as BMC Snapshot copies and are processed by the BMC AMI Recover SNAP phase.

A consistent FlashCopy is processed in the same way as a BMC Online Consistent Copy. For more information about Online Consistent Copy, see Using-Online-Consistent-Copy.
Important
Note the following considerations:
- BMC AMI Recover supports consistent FlashCopies with log apply when you do not specify INCOPY.
- BMC AMI Recover supports consistent FlashCopies with INCOPY TOCOPY specified.
- BMC AMI Recover does not support consistent FlashCopies when you specify both INCOPY and log apply (RBA or LOGPOINT specified in the INCOPY specification).
An inconsistent FlashCopy is processed as a SHRLEVEL CHANGE copy in the same manner used for inconsistent BMC Snapshot copies.
Sequential copies created from a consistent FlashCopy are processed in the same way as sequential BMC Online Consistent Copies.
Sequential copies created from an inconsistent FlashCopy are processed as SHRLEVEL CHANGE copies.

The OPTION command RESOURCE SELECTION syntax supports FlashCopy (FC) (RESOURCE-SELECTION). FlashCopy is also supported in the installation options LOCCPSEL (LOCCPSEL-FC-LP-LB) and REMCPSEL (REMCPSEL-RP-RB-FC). The default processing order for local copies is FC, LP, LB. The default processing order for remote copies is RP, RB, FC.

The FLASHCOPY option is available to the Non-registered copy or INLOG specification with INCOPY FULL (Non-registered-copy-or-INLOG-specification).

The DSNAME description of the INCOPY specification accommodates FlashCopy support (INCOPY-specification).