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Status Future consideration
Created by Guest
Created on Oct 18, 2023

Support GC-GC cascaded start option in 3 site MT sessions

When using CSM for migration scenarios in 3 site topologies, a typical approach is to migrate via PPRC Failover or HyperSwap from old MGM cascade to a new GC-GC cascade. Today, the new GC-GC cascade requires to use temporary 2 site MM sessions being started in GC mode, on top of the temporary migration Session managing the PPRC Failover/ Hyperswap from old to new primary.

Migration from or to Multi Target topologies is not supported, since sooner or later during the migration both 3 site topologies must be in cascaded mode to avoid that the limit of possible CR bitmaps on the DS8000 is exceeded.

What is needed to reduce the CSM efforts in supporting 3 site migrations is:
- Cascaded Start GC-GC in MT Sessions
- Needs to be possible from Define state (ideally from either site as defined in the session, but that is optional)
- Needs to be possible from Suspended state (to allow the original session running MGM to be suspended and started in GC- GC and support Migration Fall Back capability without full copy)

Idea priority High