MacKinney Systems, Inc.

What does 'w/31 bit PCCA' mean?

Beginning with z/OS 1.9, IBM introduced a new SYS1.PARMLIB(DIAGxx) parameter to move some control blocks accessed by our products to 31 bit storage:


Beginning with z/OS V1R12, the default location for the LCCA and PCCA is now in 31-bit virtual storage if you do not specify VIRTUAL24 or VIRTUAL31 for the structures IHALCCA and IHAPCCA. If only one standard processor is online during the IPL, the LCCA and PCCA of the IPL CPU will be in 24-bit storage regardless of the specification.

Some of our products, particularly older releases, require that these control blocks remain below the line in 24-bit storage. To keep them below the line, code this in your DIAGxx member.


You can determine which DIAG member you are using by looking at your IEASYSxx members, or by searching your syslog shortly after IPL for message IEE252I. Here is an example:


In this example, the DIAG31 member was specified, and found in VENDOR.PARMLIB. The default is SYS1.PARMLIB(DIAG00).

If you DO NOT specify the VIRTUAL24 parameter, you MUST run the minimum product release (or higher) identified in the last column of the Product Release Table.

If you DO include VIRTUAL24(...), you can still run the release identified in the last column of the Product Release Table, and you might be able to run an older release. If there is a reason you cannot upgrade to the minimum recommended release, please contact MacKinney Systems Technical support to discuss your needs.

You should note that it is not possible to change the control block locations without IPLing your system. The SET=DIAGxx console command cannot move these control blocks and the D DIAG command displays the contents of the DIAG member, not the actual location of the control blocks.