Quick Split Support

FDRINSTANT supports Hitachi ShadowImage Quick Split. With Quick Split, there is no necessity to pre-establish the ShadowImage pairs. Quick Split can establish a pair and split it, with full volume integrity, in a few seconds. This is similar to the operation of FlashCopy on IBM and compatible storage subsystems.

Unlike normal ShadowImage, where the ShadowImage PPRC pairs must be pre-established, and ShadowImage must be constantly mirroring all updates to the online volume on the PPRC mirror, Quick Split allows the ShadowImage pairs to be idle, with no overhead, until you need to create the point-in-time copy of the online volume. The ShadowImage pairs can be in simplex (not established) or suspended status up to the point of the PSPLIT; then Quick Split creates the ShadowImage mirrors in just seconds per volume.

JCL changes for ABR

Invoking Quick Split with PGM=FDRABR is easy. Simply add this DD statement to any FDRINSTANT PSPLIT step and any FDRABR DUMP step that has PPRC= on the DUMP statement:

//FDRPPQAS DD DUMMY

The presence of this DD statement causes FDRINSTANT to invoke Quick Split on ShadowImage pairs.

If you have ICKDSF steps to ESTABLISH and SUSPEND the ShadowImage PPRC pairs, you can discard those steps; they are no longer required.

In an FDRINSTANT PSPLIT step, your MOUNT statements must specify VOL= and PPRCUNIT=, for example

MOUNT VOL=DB2005,PPRCUNIT=3C54

And there must be one MOUNT statement for each volume involved. This is required since Quick Split does not require any preexisting ShadowImage relationship between the online volume and its ShadowImage mirror, so the PPRCUNIT= parameter must be used to specify the ShadowImage device.

In an FDRINSTANT DUMP step, we recommend using PPRC=USE instead of PPRC=(USE,RET). PPRC=USE will leave the ShadowImage pairs in a suspended state after the dump is complete; this is preferable for use with Quick Split as described below.

Quick split operation for ABR

In the FDRINSTANT PSPLIT step:

If there is no existing ShadowImage relationship between the online DASD and the ShadowImage mirror (“simplex” status), then the PSPLIT step does a “Quick Add and Split”. This establishes a ShadowImage relationship between the volumes and splits it immediately without waiting for the volumes to synchronize. ShadowImage guarantees that the ShadowImage volume can be read as if it were a full point-in-time copy of the online volume.
If the online volume and the ShadowImage mirror are in “suspend” status (in a relationship but not currently being updated), then the PSPLIT step does a “Quick Re-sync and Split”, similar to a “Quick Add and Split”.
If the pair is currently in “pending” status, synchronizing after a normal ShadowImage PPRC ESTABLISH, the PSPLIT waits for the synchronization to complete, which may take a few minutes.
If the pair is already established (in “duplex” mode), a normal split is done.

Normally the pair is in one of the first two states, simplex or suspended, so Quick Split allows the ShadowImage point-in-time image to be created in only a few seconds per volume.

In the FDRINSTANT DUMP step, if PPRC=(USE,RET) is specified, a “Quick Re-sync” is done after the dump is complete to put the ShadowImage volumes back in duplex status. However, duplex means that ShadowImage is constantly mirroring the online volume to the ShadowImage volume and this is not necessary with Quick Split. So it is recommended that you use PPRC=USE instead of PPRC=(USE,RET).

ABR Quick Split example

Here is an example of a Quick Split job for ABR incremental backup, copied from “ABR Incremental Backup Example” in Section 27.3. The only difference is the addition of the FDRPPQAS DD statement to the PSPLIT and DUMP steps:

//INCR1 EXEC PGM=FDRABR,REGION=0M //SYSPRINT DD SYSOUT=* //SYSPRIN1 DD SYSOUT=* //FDRSUMM DD SYSOUT=* //SYSUDUMP DD SYSOUT=* //TAPE1 DD DUMMY //FDRPPQAS DD DUMMY //SYSIN DD * PSPLIT TYPE=ABR,DSNENQ=USE,RETPD=14,ENQERR=NO MOUNT VOL=CICS01,PPRCUNIT=01F2 MOUNT VOL=CICS02,PPRCUNIT=01F3 /* //* //INCR2 EXEC PGM=FDRABR,REGION=0M //SYSPRINT DD SYSOUT=* //SYSPRIN1 DD SYSOUT=* //FDRSUMM DD SYSOUT=* //SYSUDUMP DD SYSOUT=* //FDRPPQAS DD DUMMY //TAPE1 DD DSN=ABR1,UNIT=CART,DISP=(NEW,KEEP) //SYSIN DD * DUMP TYPE=ABR,DSNENQ=USE,RETPD=14,ENQERR=NO, PPRC=USE,RTC=YES MOUNT VOL=CICS01 MOUNT VOL=CICS02 /*

Quick Split with FDR, FDRDSF, and FDRCOPY

Quick Split can be used with FDRINSTANT for FDR, FDRDSF, and FDRCOPY, but you must invoke the Quick Split manually.

ShadowImage-for-ABR shows example jobs for FDRINSTANT, including ICKDSF PPRCOPY SUSPEND or ESTPAIR commands executed before the FDR steps. To use Quick Split, use an ICKDSF PPRCOPY ESTPAIR command with special values in the PRI operand. Replace the “serial number” (the second sub-operand of PRI) with:

MSF00 – If the online volume is currently in SIMPLEX status (not paired). This invokes a Quick Add and Split.
MRF00 – If the online volume is currently in SUSPEND status (split). This invokes a Quick Re-sync.

For example,

//SYNC EXEC PGM=ICKDSF //SYSPRINT DD SYSOUT=* //DISK1 DD UNIT=SYSALLDA,VOL=SER=CICS01,DISP=OLD //DISK2 DD UNIT=SYSALLDA,VOL=SER=CICS02,DISP=OLD //SYSIN DD * PPRCOPY ESTPAIR DDNAME(DISK1) PRI(X’0080’,MSF00,X’13’) - SEC(X’0080’,30158,X’32’) LSS(X’01',X'01') PPRCOPY ESTPAIR DDNAME(DISK2) PRI(X’0080’,MSF00,X’17’) - SEC(X’0080’,30158,X’33’) LSS(X'01',X'01') /*

This can be executed immediately before the FDR, FDRDSF, or FDRCOPY step that references the ShadowImage mirror. There is no need to wait for the mirror to be synchronized; the point-in-time data is available immediately.