Plan for the increase of the maximum number of supported CPUs to 256

Description

In z/OS V2R2, z/OS CPU infrastructure supports up to a maximum of 256 CPUs (CPU IDs 0-255). Earlier releases of z/OS support up to 100 CPUs (CPU IDs 0-99). Components or products allocating storage for CPU related arrays or bitmasks might require changes to support the V2R2 CPU infrastructure.

Allocating CPU related arrays or bitmasks on a per CPU basis is done using one of the following:
  • Runtime fields in the z/OS CVT (mapped by CVT) and ECVT (mapped by IHAECVT) control blocks representing the maximum CPU ID a z/OS image can use for the life of the IPL. Products using runtime fields do not require changes to support the V2R2 CPU infrastructure.
  • Compile-time or assemble time constants in the z/OS ECVT control block or within the product itself representing the maximum CPU ID the z/OS CPU infrastructure supports. Products using compile-time or assemble time constants need to recompile at a minimum, and might require code changes to support the V2R2 CPU infrastructure.

All products running on z/OS V2R2 must prepare to support all CPUs supported by the z/OS V2R2 CPU infrastructure (up to 256 CPUs with CPU IDs 0-255). Products that support the z/OS V2R2 CPU infrastructure will be able to run on earlier z/OS releases whose CPU infrastructure supports a smaller number of CPUs.

Table 1 provides more details about this 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 V2R1.
Applies to migration from: z/OS V1R13.
Timing: Before the first IPL of z/OS V2R2
Is the migration action required? Yes, for programs using local constants or the z/OS constants for the number of CPUs the z/OS CPU infrastructure supports at the current or a specific level of z/OS
Target system hardware requirements: None.
Target system software requirements: None.
Other system (coexistence or fallback) requirements: None.
Restrictions: None.
System impacts: Programs that do not support up to the maximum number of CPUs the z/OS infrastructure supports might not be able to work with all CPUs on the z/OS image. The system impacts are program dependent.
Related IBM Health Checker for z/OS check: None.

Steps to take

Follow these steps:
  • Scan your code for all of the constants in the ECVT control block that have a prefix of ECVT_max_* or ECVT_zOSR11_*. These fields are all related to the maximum CPU ID the current or a specific z/OS release supports.
  • Scan your code for compile-time or assemble-time constants in your product for constants related to the maximum CPU ID that the current or a specific z/OS release supports. Also scan your product for constants related to the maximum number of CPUs the current or a specific z/OS release supports.
If you use ECVT constants with a prefix of ECVT_max_* or ECVT_zOSR11_* , the product will require the following changes:
  • If the ECVT_zOSR11_highestCPUID or ECVT_max_highestCPUID constants are in use:, consider upgrading your code to use the run-time field CVTMAXMP (for allocating CPU related arrays) or ECVT_Installed_CPU_HWM (for traversing CPU related arrays). •
  • If ECVT compile-time or assemble-time constants with a prefix of ECVT_max_* are in use, recompile/reassemble all appropriate parts with the z/OS V2R2 IHAECVT macro.
  • If ECVT compile-time or assemble-time constants with a prefix of ECVT_zOSR11_* are in use, consider converting constants with a prefix of ECVT_zOSR11_* to the ECVT_max_* analog. Otherwise change ECVT_zOSR11_* to the new ECVT_zOSV2R2 analog.
If your code has its own local declares for compile-time or assembler-time constants, update your code to use the z/OS run-time fields or the z/OS compile-time or assemble-time constants. Do the following:
  1. Allocate CPU bit masks at compile-time or assemble-time using ECVT_max_CPUMaskSizeInBits or ECVT_max_CPUMaskSizeInBytes.
  2. Convert to using run-time fields like CVTMAXMP to allocate your local CPU related arrays. If using run-time fields is undesirable, allocate CPU arrays using the compile-time or assemble time constants ECVT_max_* or ECVT_zOSV2R2_* fields

Reference information

For more information, see z/OS MVS Data Areas in the z/OS Internet library.

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