Incremental flashcopy function – HP StorageWorks XP Remote Web Console Software User Manual
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Figure 18 Using a Consistency Group with Version 2: Copying Multiple Data that is Stored over
Multiple Volumes
shows copying data stored over volumes #1 through #3 to volumes #4 through #6.
You need to first establish relationships between volumes #1 and #4, #2 and #5, and #3 and #6,
and then copy the data. However, if volume #1 is updated before the creation of Relationship B
(the pair of #2 and #5) is completed, the consistency of the data in the copy target cannot be
maintained.
shows Data 2 in volume #2, references Data 1 in volume #1, and Data 3 in volume
#3 references Data 2 in volume #2. Therefore, when you try to copy Data 1 through 3 to volumes
#4 through #6, if Data 1 is updated before the copying processing of Data 2 is completed, the
consistency of copied Data 1 and copied Data 2 cannot be maintained.
To prevent these problems, Version 2 regards volumes #1 through #3 as one consistency group,
and allows you to suspend the write operation from the host to the Version 2 S-VOLs until
Relationship A, Relationship B, and Relationship C are all created and all the copying processing
is finished. To suspend the write operation from the host to Version 2 S-VOLs by using consistency
groups, you need to issue the pair creation command with an option parameter. For information
about the relationship establishment command and the option parameter, see
.
When Version 2 and TrueCopy for Mainframe share volumes, the results of operations such as
creating pairs will differ depending on whether you are using a consistency group or not.
Incremental FlashCopy Function
Incremental FlashCopy maintains a relationship even after the copy operation from copy source
to target is completed. Later, when the S-VOL or T-VOL is updated, the updated data is managed
in a track as differential data. If the command to establish a relationship is re-executed on the
volumes originally related using the Incremental FlashCopy function, only differential data is copied.
shows the workflow from the establishing of the relationship (using Version 2) to the
executing of the update copy operation using the Incremental FlashCopy function.
Incremental FlashCopy Function
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