The JES2 patching facility

Patch and AMASPZAP statements can be used to make minor and temporary modifications to the JES2 object code until JES2 is restarted by directly replacing the changed code. The JES2 Patching Facility changes only the memory copy of data; the copy residing on DASD (for example, LPA) cannot be replaced.

The JES2 patching facility makes temporary patches to any module in JES2 (HASJES20 or installation exit load module) or to any absolute storage address in the address space into which JES2 is loaded. Because these patches are valid only until a module is reloaded, they must be applied every time that JES2 is started.

JES2 reloads the load modules at different stages in processing:

Subsystem support modules are reloaded during all starts except a hot start.
HASJES20 is reloaded in response to a JES2 START command any time the member is started.

These patches are applied at the time JES2 is initialized. The patching facility statements are submitted to the JES2 initialization data set.

There are two basic patching formats:

Using the NAME initialization statement to specify the module name
Specifying the module name in the VER initialization statement.

Note: If you specify the module name in both the NAME and the VER initialization statement, JES2 cannot patch the data.

For more directions on how to code the patch statements, see the NAME, REP, and VER initialization statements in z/OS JES2 Initialization and Tuning Reference. Directions for using the AMASPZAP program are provided in the "SPZAP" topic in z/OS MVS Diagnosis: Tools and Service Aids. JES2 processes the patch and AMASPZAP statements as they are read.