A message is any piece of information that you want to transmit in an active group from one member to another. The data that makes up the message is of interest to the multisystem application only and not to z/OS®.

A message can vary in length up to 128M bytes and resides in the storage area of the sending or receiving member. The data that makes up the message can reside in a single buffer or in multiple buffers. An additional 32 bytes of control information can be associated with each message.