XMEMOPT parameter

Cross-memory PC options

Summary

Default value

X'02' if M204XSVC is linked into the nucleus

X'00' if M204XSVC is not linked into the nucleus

Parameter type

System

Where set

On User 0's parameter line

Related products

All

Introduced

Model 204 V6.1 or earlier

Description

This parameter sets the Model 204 cross-memory services options that can be invoked during execution of Model 204.

This parameter applies only to z/OS.

The XMEMSVC parameter is used with any of the nonzero settings.

Valid settings of XMEMOPT are:

Setting	Meaning
X'80'	Activates CRAM-XDM. If the Online and CRAM-XDM load modules are not APF authorized, the X'80' bit is turned off.
X'20'	Use SUSPEND/RESUME instead of WAIT/POST for communication between Model 204 real subtasks. This option may reduce operating system overhead slightly. If the Online load module is not APF authorized, the X'20' bit is turned off.
X'04'	Forces initialization of cross-memory environment (M204XSVC).
X'03'	Invokes both Timer PC and IOS Branch Entry.
X'02'	Invokes IOS Branch Entry (recommended for z/OS) to handle all database and CCATEMP I/O. If the Online load module is not APF authorized, the X'02' bit is turned off. As of Model 204 version 7.6, the X'02' setting is required for zIIP processing and for allocating Model 204 buffer pool buffers above the bar.
X'01'	Invokes Timer PC. Note: As described in the Timer PC section, this bit is automatically turned off as of version 7.4 of Model 204 if your system supports the ECTG instruction.
X'00'	Disables Model 204 cross-memory services.

Note: VIO is incompatible with IOS Branch Entry and EXCPVR.