Regarding SRDF/A and SRDF/S mode?

You can use the cocsistency exempt feature to add/remove devices from an SRDF/A group. to add devices, create a new RDF group and put your new devices in there, synch them up in  adaptive copy. Then use move pair with the consistency exempt feature to put them into your SRDF/A group.

This discussion may help:

https://community.emc.com/message/534549#534549

SPLIT=R2 device is RW enabled.

SUSPEND= R2 device remains NR or WD.

• Create a new set of replication with the devices you want to, have separate RDF group
• Initial replication with adaptive copy disk mode to avoid SRDF link bottlenecks
• Once the data’s synchronized set the mode async
• Use consist_excempt feature to move the new pair from current RDF group to existing RDF group in which the SRDF/A is happening
• And Verify

Suspend – This command maintain the R1/R2 device status as it is,  but the link will become ready and no data will be moved across the SRDF link. When you resume the replication then the data will flow from R1 to R2

Split – If both R1 & R2 devices are host configured, upon split command both the devices will be ready for host read / write operation. The link will be not ready. In this state you  can bring R2 data to R1, or the R1 data to R2.