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54 IBM System Storage DS6000 Series: Copy Services with IBM System z
7.1 Multiple relationship FlashCopy
It is possible to establish up to 12 FlashCopy relationships using the same source. In other
words, a source volume can have up to 12 target volumes. However, a target volume can still
only have one source. Furthermore, cascading FlashCopy is not allowed (that is, a volume
cannot be both a source and a target volume).
Following is a summary of the considerations that apply:
A FlashCopy source volume can have up to 12 FlashCopy target volumes.
For each source volume, only one FlashCopy relationship can be reversed (the one that
has been established with the TSO FCESTABL command and INCREMENTAL(YES)
option).
A FlashCopy target volume can have only one FlashCopy source volume.
A FlashCopy target volume cannot be a FlashCopy source volume at the same time.
Figure 7-1 illustrates what is possible and what is not with multiple relationship FlashCopy.
Figure 7-1 Multiple relationship FlashCopy possibilities
Multiple relationship FlashCopy at the data set level
Multiple relationship FlashCopy is also supported at the data set level, though not all
interfaces that support the multiple relationship FlashCopy will support multiple relationships
at the data set level. In Figure 7-8 on page 61 we see that neither the DS Storage Manager
nor the DS CLI support multiple relationships at the data set level. Also in Figure 7-8 on
page 61, as stated in Note 1, it is important to point out that though TSO and the ANTRQST
Note: Only one of those targets can be defined as incremental FlashCopy.
Note: At any point in time, a volume, or a data set, can only be a source or a target.
source
target
FlashCopy
maximum is 12
...
...
source
target
FlashCopy
not allowed
a source can have up to
12 targets
a target can have only
one source
source
target
FlashCopy
not allowed
a volume or dataset can be only a
source or target at any given time
source and
target