IMS/DC Parameter Relationships

The cross-memory IMS/DC access involves up to three different address spaces as follows:

IMS/DC message processing region address spaces
The user's IMS/DC transaction resides here. If multiple IMS/DC users are processing concurrently (input being processed by the XMS system), a separate IMS/DC message region is used for each user.

IMS/DC can control the maximum number of IMS/DC transactions executing at one time.
The XMS support subtask
- The subtask is started when the XMSSUB=YES input parameter is used when an XMS address space is started.
- The subtask can be in a separate XMS address space or share the address space with XMS or VTAM sessions.
- The XMSSUB=YES must only be used in an XMS address space with a default subsystem ID (SUBSYS=XMC0 or not specified).
- If multiple XMS address spaces are started, only one can have the XMSSUB=YES specified.
Note: All IMS/DC, TSO/XMS, ISPF/XMS and CA Roscoe/XMS sessions share the same XMS subtask.
XMS address spaces
See the topic that follows.