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

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 V2R1 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 V2R1 CPU infrastructure.

All products running on z/OS V2R1 must prepare to support all CPUs supported by the z/OS V2R1 CPU infrastructure (up to 256 CPUs with CPU IDs 0-255). Products that support the z/OS V2R1 CPU infrastructure will be able to run on earlier z/OS releases whose CPU infrastructure supports a smaller number of CPUs.

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 new z/OS V2R1 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_zOSV2R1 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_zOSV2R1_* fields