HP XP Business Copy Software - Manual (Page 107)

ShadowImage for z/OS user guide 107
Figure 52 Ex. Consist. Group w/FlashCopy(R) Mirror Ver. 2: Copying Mult. Data Stored over Mult. Vols.
Figure 51 illustrates the example of copying the data stored over the volumes #1-#3 to the volumes #4-#6.
You need to create pairs of volume #1 and #4, #2 and #5, and #3 and #6, then copy the data. However,
if the volume #1 is updated before the creation of the Pair B (pair of #2 and #5) completes, the
consistency of the data in the copy target cannot be maintained.
In,
Figure 52 , Data 2 in the volume #2 references Data 1 in the volume #1, and Data 3 in the volume #3
references Data 2 in the volume #2. Therefore, when you try to copy Data 1-3 to the volume #4-#6, if Data
1 is updated before the copying processing of Data 2 completes, consistency of copied Data 1 and
copied Data 2 cannot be maintained.
To prevent the abovementioned problems, FlashCopy Mirror Version 2 regards volumes #1-#3 as one
consistency group, and allows you to suspend the write operation from the host to the FlashCopy Mirror
Version 2 S-VOLs until the Pair A, Pair B, Pair C are all created and all the copying processing is finished.
To suspend the write operation from the host to FlashCopy Mirror Version 2 S-VOLs by using consistency
groups, you need to issue the pair creation command with an option parameter. For information about the
pair creation command and the option parameter, see ” TSO Command Supported by Compatible
Mirroring for IBM FlashCopy Version 2 ” on page 132. For the information about the example of using the
command, see ” Creating FlashCopy Mirror Version 2 Pairs: FCESTABL ” on page 135.
NOTE: When FlashCopy® Mirror Version 2 and TCz share volumes, the results of operations such as
creating pairs will differ according to whether you are using a consistency group or not. For details,
” Combining Compatible Mirroring for IBM® FlashCopy® Version 2 With ShadowImage for z/OS® ” on
page 117.
Incremental FlashCopy Function
The Incremental FlashCopy allows you to maintain a relationship even after the copy operation from the
copy source to the copy target is completed. Also, when the S-VOL or the T-VOL is updated during or after
the copy operation, the updated part will be managed in a track as differential data. If you re-execute the
command to establish a relationship on the relationship established by the Incremental FlashCopy function,
only the differential data will be copied. The following figure shows the workflow from the establishing of