REP - Replacing Code Through the JES2 Patching Facility

The REP initialization statement is one of several statements used by the JES2 patching facility. For the other statements, see VERify - Verifying Code Through the JES2 Patching Facility and NAME - Naming the Module to Change Through the JES2 Patching Facility. The JES2 patching facility allows you to specify temporary replacement data (patches) for the following:

• Any module in JES2 (HASJES20 or an installation exit load module)
• Any absolute storage address from the address space where JES2 is loaded.
• On a hot start, any address in a data space created by JES2 (that is, owned by JES2AUX)
• On any warm start, any address in the JES2 checkpoint data set.

Patching facility statements are placed in the JES2 initialization data set and applied when JES2 is initialized. The JES2 patching facility applies temporary patches to the in-storage copy of JES2 modules. Because some of the initialization code has already been executed before the patch facility initialization statements are processed, patches made to those portions of the code are ineffective; those portions of code do not execute again until you restart JES2. Most patches are applied immediately as the statements are processed. However, checkpoint updates are deferred until the checkpoint record is read. Non-checkpoint patches are not saved across a warm start. JES2 reloads the load modules at different stages in processing:

• Subsystem support modules are reloaded during all starts except a hot start.
• HASPJES20 is reloaded in response to a JES2 START command any time the JES2 member is started.

In addition, you should be aware that the JES2 patching facility does not support:

• Patching a module or data area residing in read-only storage. For example, you cannot use the facility to modify modules in PLPA or PSA.
• Patching a HASPFSSM load module that has been loaded into a functional subsystem address space. Use AMASPZAP (the service aid program that modifies both instructions and data) to patch the HASPFSSM load module.
• Altering the JES2 dump formatting exit modules (HASMxxxx).
• Using a patch across a restart of JES2. Because these patches are valid only until a load module is reloaded, they must be reapplied every time JES2 is started.