Modified Link Pack Area (MLPA)

It’s defined in SYS1.PARMLIB(IEALPAxx).
Can be used to contain reenterable load modules from APF-Authorized libraries that are to be part of the pageable extension to the Link Pack Area (LPA) during the current IPL.
Can only have PDS files. PDS/Es are not allowed.
LPA modules that have been replaced through IEALPAxx are not physically removed from the PLPA or from the PLPA directory. They are however, logically replaced, because when one of them is requested, MLPA is searched first and then the system does not examine the LPA directory that contains the name of the replaced module.
The system searches FLPA before MLPA for a particular module and selects the module from MLPA only if the module is not also in the FLPA.
You may use IEALPAxx to temporarily add or replace SVC or ERP routines. Another possible application would be the testing of replacement LPA modules that have been altered by PTFs.
Modules with an RMODE of 24 are placed in the MLPA, while those with an RMODE of ANY are placed in the extended MLPA.