Coupling XRC sessions

Use the XCOUPLE ADD command to couple an XRC session to a master session. The first time you issue this command for a session, XRC creates a new member in the session's state data set to indicate that the session is coupled to the specified master session. The member is also used during XSTART processing to determine if the session is to be recoupled to a master session. The XCOUPLE ADD command may only be invoked against XRC sessions that have been started with the SESSIONTYPE(XRC) parameter.

You can couple multiple SDMs within a logical partition to the same master session through a cluster session. Specifying the master name on the XRC PARMLIB parameter of ClusterMSession enables a cluster session for a logical partition, and all XCOUPLE ADD commands issued on this logical partition cause the SDMs to be coupled to the same master session through the cluster session.

Note: You should not start multiple SDMs in the same logical partition unless you have sufficient real storage to support them. A busy SDM can effectively consume all usable storage in a 2 GB storage configuration. Starting multiple SDMs and coupling them together in this environment can cause a negative performance impact.

Recommendation:The best performance can be achieved by ensuring that all volumes in a data mover session are in DUPLEX state prior to coupling the data mover session to a Master session. The time for the volumes to reach DUPLEX state in an uncoupled data mover can be up to 50% faster than the time for volumes in a coupled data mover to reach DUPLEX state.