Assess the use of the INCLUDE1MAFC keyword on the LFAREA parameter in IEASYSxx

Description

Prior to z/OS® V2R2, the default was for RSM not to include 1 M fixed frames in the available frame count (RCEAFC). APAR OA41968 added the INCLUDE1MAFC keyword on the LFAREA parameter in the IEASYSxx member of parmlib to cause RSM to include 1 M fixed frames in the available frame count. This results in the following system behavior:
  • RSM performs less paging when there is an abundance of available 1 M fixed frames in the system.
  • RSM is more likely to break up 1 M fixed frames to satisfy 4 K page demand. Although RSM attempts to coalesce broken up 1 M fixed frames when there is fixed 1 M page demand, there is no guarantee that coalescing will be successful, especially if any of the 4 K frames making up the fixed 1 M page is fixed long term.

Starting with z/OS V2R2, RSM includes 1 M fixed frames in the available frame count by default; you no longer need to specify INCLUDE1MAFC to do this. Furthermore, the syntax of the INCLUDE1MAFC keyword has been extended to include a YES or NO option. The former INCLUDE1MAFC keyword syntax is still valid and can now also be specified as INCLUDE1MAFC(YES).

IBM recommends that you accept the default (or specify INCLUDE1MAFC or INCLUDE1MAFC(YES)). However, if you have a need to retain the old default behavior (that is, to exclude 1 M fixed frames from the available frame count), you must specify INCLUDE1MAFC(NO).

Table 1 provides more details about the migration action. Use this information to plan your changes to the system.

Table 1. Information about this migration action
Element or feature: BCP.
When change was introduced: z/OS V2R2.
Applies to migration from: z/OS V2R1 and z/OS V1R13.
Timing: Before the first IPL of z/OS V2R2.
Is the migration action required? Yes, if you did not specify the INCLUDE1MAFC keyword on the LFAREA parameter in IEASYSxx prior to z/OS V2R2 and you want to continue excluding 1 M fixed frames from the available frame count.
Target system hardware requirements: None.
Target system software requirements:
  • RMF APAR OA42066 for z/OS V2R1
  • RMF APAR OA42510 for z/OS V1R13
Other system (coexistence or fallback) requirements: None.
Restrictions: None.
System impacts: None.
Related IBM® Health Checker for z/OS check: None.

Steps to take

Follow these steps:
  • Check the LFAREA parameter specification in the IEASYSxx member on your pre-z/OS V2R2 system.
    • If you specified the INCLUDE1MAFC keyword on the LFAREA parameter after APAR OA41968, and you want to continue with that setting on your z/OS V2R2 system, you can do any of these things:
      • Leave the INCLUDE1MAFC keyword as it is.
      • Remove the INCLUDE1MAFC keyword, as it is now the default.
      • Change INCLUDE1MAFC to INCLUDE1MAFC(YES).
    • If you did not specify the INCLUDE1MAFC keyword on the LFAREA parameter and you want to retain the old default behavior, you must now specify INCLUDE1MAFC(NO).
  • Check any application programs that use the STGTEST SYSEVENT to determine if any changes need to be made. The STGTEST event returns information about the amount of storage available in the system, which includes the LFAREA when INCLUDE1MAFC(YES) is specified or defaulted. Application programs can check the RCEINCLUDE1MAFC bit to determine the setting of INCLUDE1MAFC in the LFAREA specification.

Reference information

For information about the LFAREA parameter and the INCLUDE1MAFC keyword in IEASYSxx, see z/OS MVS Diagnosis: Tools and Service Aids.

Parent topic: BCP actions to perform before the first IPL of z/OS V2R2