IMS Notes (New Version)

Be aware of the following:

The new IMS/DC Transaction Program (EC2XMIMS) is a replacement for the older SARXMIMS program.
The EC2XMIMS does not need to be linkedited to the ASMTDLI interface program. The transaction is now conversational with a SPASIZE=18 (this can be adjusted).
If you use extended color, the SEGSIZE= may need to be increased, because extended color data streams can be a 50% increase over the monochrome data stream size.
To determine the SEGSIZE= value, take the terminal that uses the interface with the largest screen size, in bytes, and apply the following formula:
```
ROWS * COLS * 1.5 = SEGSIZE
```
For example, a 3278-5 with a 27 x 132 screen size would be (27 * 132 * 1.5) = 5346. If the SEGSIZE= is too small, the terminal user will get an RC= "A6" message indicating that a message insert failed.

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=XMC2 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.