CICS Program Residency for Ideal, IPC, and VPE

Products

• Datacom
• Ideal
• IPC
• Datacom/DB

Issue/Introduction

Which Ideal, IPC, and VPE programs must be marked resident?

Environment

Component : CAIVPE

Component : Datacom/DB

Resolution

Before producing this list, it is important to raise a warning regarding the possibility that performance will suffer if this is not done properly. Some programs are chosen for residency because Ideal, IPC and VPE count on them to remain at a fixed address. Making these programs non-resident will eventually lead to random ASRA abends or storage violations. Other programs are made resident because they are "VPE globally loaded". The use count is altered to ensure they always remain in storage even if they are specified as RES=NO. Under CICS, an EXEC CICS LOAD HOLD command is issued. Specifying RES=NO in these instances will actually increase the amount of storage used. Other programs are chosen for residency because they are very small. Making small programs non-resident will cause each module to use a page of storage when loaded instead of being able to fit several on a single page. That means if at any time more than one of these modules is in storage, a non-resident load will actually require more storage in the CICS region.

Last, but not least, some programs are resident because they are highly used. So be very careful! Several clients have reported performance degradation after modifying the residency of the PPTs distributed for Ideal, IPC, and VPE.

Each program specified below is designated as either "required" or "global load". The "required" programs MUST maintain RES=YES on the PPT entry, and the "global load" programs should maintain RES=YES on the PPT entry for the reasons stated above.

Ideal programs
@IADTREX	REQUIRED
@IADCMDI	GLOBAL LOAD
@IAEPNEX	GLOBAL LOAD

 

IPC programs
SCF	SC00CVTP	REQUIRED
	SC00TRAN	REQUIRED
	SC00SECR	REQUIRED
PSS	SCPSMAIN	REQUIRED
PMS	PMSPNS1	REQUIRED
	PMSEDIT	REQUIRED
	PMSTBLS	REQUIRED
	PMSTRUC	REQUIRED
	PMSTRND	REQUIRED
	PMSV#R#	GLOBAL LOAD
	PMSTBLS	GLOBAL LOAD
VPE	VPEKTHS	REQUIRED