Chapter 11. Advanced Copy Services 453
Figure 11-12   Consistency groups and mappings combinations
When a source volume is in a FlashCopy mapping with multiple targets, in multiple 
consistency groups, it allows the copy of a single source at multiple points in time. Therefore, 
multiple versions of a single volume are kept.
Consistency Group with Multiple Target FlashCopy
A Consistency Group aggregates FlashCopy mappings, not volumes. Therefore, where a 
source volume has multiple FlashCopy mappings, they can be in the same or separate 
Consistency Groups.
If a volume is the source volume for multiple FlashCopy mappings, you might want to create 
separate Consistency Groups to separate each mapping of the same source volume. 
Regardless of whether the source volume with multiple target volumes is in the same 
consistency group or in separate consistency groups, the resulting FlashCopy produces 
multiple identical copies of the source data.
Dependencies
When a source volume has multiple target volumes, a mapping is created for each 
source-target relationship. When data is changed on the source volume, it is first copied on 
the target volume because of the copy-on-write mechanism that is used by FlashCopy. 
You can create up to 256 targets for a single source volume. Therefore, a single write 
operation on the source volume might result in 256 write operations (one per target volume). 
This generates a large workload that the system cannot handle and lead to a heavy 
performance impact on front-end operations.