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290 IBM System Storage DS6000 Series: Copy Services with IBM System z
FRR replicates all data from C to B making a physical copy of C, with some exceptions. Note
that the previous
nocopy relationship between B and C caused some I/Os from B to C.
Changed tracks between two Consistency Group creation points will be preserved on the C
volume after being copied over from the B volumes before they change there.
These tracks arrive at the C volume between Consistency Group formation and do not
contribute to a consistent state because not all required data is physically on the C volume.
So after the FRR-triggered background copy from C to B completes, the C volume is actually
not usable. You need another step to establish another FlashCopy from B to C to make both
volumes really identical. This FlashCopy may be the one you use to create a Global Mirror
environment and is going to position the Global Mirror session for a following restart.
But first we perform the FRR from C to B. Example 23-9 illustrates how to do it when using
TSO commands.
Example 23-9 Create a consistent set of B volumes
//* ---------------------------- TSO ------------- FAILOVER (4) -- ***
//* FLASHCOPY C -> B FAST REVERSE RESTORE (BACKGROUND COPY C -> B) ***
//* 3E00 -> 3C00 ***
//* ***
//* NOTE: WAIT TILL ALL BACKGROUND COPIES COMPLETED BEFORE CONT. ***
//* NOTE: FRR DOES NOT ALLOW REMOTE(YES) ***
//* -------------------------------------------------------------- ***
//FCFRR EXEC PGM=IKJEFT01
//SYSPRINT DD SYSOUT=*
//SYSTSPRT DD SYSOUT=*
//SYSTSIN DD DDNAME=SYSIN
FCESTABL SDEVN(X'3E00') TDEVN(X'3C00') ACTION(FRR)
Note that the FlashCopy source volume for this command is the former FlashCopy target
volume and vice versa. ACTION(FRR) combines all particular FlashCopy attributes for this
action into this single parameter.
You have to wait until all FRR operations complete successfully, before proceeding with the
next step. Note that when the background copy completes, the FlashCopy relation will end.
This is what you may query to determine when all FRR operations are complete.
23.7.6 Reestablish the FlashCopy relationship between B and C volumes
In this step you establish the former FlashCopy relationship between the B and C volumes, as
it was at the beginning when you set up the Global Mirror environment. This step is in
preparation for returning later to production at the local site. The command at this step,
illustrated in Example 23-10, is exactly the same FlashCopy command you may have used
when you initially created the Global Mirror environment. See 22.3.4, “Introduce FlashCopy”
on page 257.
Example 23-10 Reestablish FlashCopy between B and C volume with MODE(ASYNC)
//* ---------------------------- TSO ------------ CREATE (3) ----- ***
//* FLASHCOPY B -> C START CHANGE RECORDING NOCOPY ETC. THROUGH ***
//* MODE(ASYNC) OPTION (GET READY FOR GM) ***
//* -------------------------------------------------------------- ***
//* SOURCE AND TARGET REQUIRED ***
//* -------------------------------------------------------------- ***
//FCESTBL EXEC PGM=IKJEFT01
//SYSPRINT DD SYSOUT=*
//SYSTSPRT DD SYSOUT=*