DS8A hardware support for a Copy target to be the source for multi target copy relation

Note:

This case describes the need within a MGM4 solution, but could apply to certain setup in other 3-4-6 site solutions as well.

We are in the progress of moving to a MGM4 solution with copy relation A-B-C-D.

A C
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B D

In current design we can only maintain our (physical isolated) LCP in the secondary region (region B) behind the D-disk. This provides 3 blocking issues:

1. When performing a planned or unplanned region swap to C-D-A-B, the LCP in Region B behind the D-disk cannot take any new captures. At that moment LCP processing in Region A behind the B-Disk must start from scratch.
   This provides a risk when at that time you would require a validation and restore from cybervault as most recent captures are in Region A and older captures are in Region B. Also surgical restore would be problematic.

2. In normal operation, when running from Region A or from Region B, you would need a Region swap in order to be able to restore from cybervault.

3. In case of a secondary site failure in your secondary region, you will loose all of your cybervault recovery possibilities.

We need a symmetrical LCP set-up where we have an active (physical isolated) LCP behind B-Disk and D-Disk, no matter in which region we run and which Site is the primary.

A C
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B D
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LCP_REGA LCP_REGB

So in an A-B-C-D copy relation, a multi target copy relation must be possible from B-C and from B-LCP_REGA

(and the same in C-D-A-B copy relation, a multi target copy relation must be possible from D-A and from D-LCP_REGB)

Also a 3-way Copy relation is needed, because after a Site switch from A-B when running in Region A, the B-Disk would become the source for copy relations B-A, B-C and B-LCP_REGA.

(And the same for after a Site switch from C-D when running in Region B, where the D-Disk would become the source for copy relations D-C, D-A and D-LCP_REGB.)

For this we need:

1. DS8A hardware support for a Copy target to be the source for multi target copy relation. (Known as Y solution)
   Idea https://ideas.ibm.com/ideas/ZGDPS-I-372

2. GDPS support for a Copy target to be the source for multi target copy relation.
   Idea https://ideas.ibm.com/ideas/ZGDPS-I-373

3. DS8A hardware support for a 3-way Copy relation.
   Idea https://ideas.ibm.com/ideas/DS80-I-324

4. GDPS support for a 3-way Copy relation.
   Idea https://ideas.ibm.com/ideas/ZGDPS-I-325