Planning for 31-bit addressing

Most programs that run on MVS/370 will run in 24-bit addressing mode without change. Some programs need to be modified to execute in 31-bit addressing mode to provide the same function. Still other programs need to be modified to run in 24-bit addressing mode.

The MVS™ conversion notebook helps you identify programs that need to be changed. You will need to consult one or more versions of the MVS conversion notebook. The versions you need depend on your current version of MVS and the version of MVS to which you are migrating. See the appropriate version of the MVS conversion notebook for your migration.

Planning for 31-bit addressing helps you determine what changes to make to a module you are converting to 31-bit addressing and indicates 31-bit address considerations when writing new code.

Some reasons for converting to 31-bit addressing mode are:

The program can use more virtual storage for tables, arrays, or additional logic.
The program needs to reference control blocks that have been moved above 16 megabytes.
The program is invoked by other 31-bit addressing mode programs.
The program must run in 31-bit addressing mode because it is a user exit routine that the system invokes in 31-bit mode.
The program needs to invoke services that expect to get control in 31-bit addressing mode.