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Like the link pack area (LPA), the modified link pack area (MLPA), option 3.5, can be used for reentrant modules from selected system or user libraries. MLPA acts as an extension to PLPA, and it exists only for the duration of the current IPL. The MLPA is not saved from one IPL to another as the LPA is. MLPA modules do not have to be read‑only and they can be modified. The principal use of MLPA is to test modules before adding them to PLPA. FLPA exists solely as a performance feature. The FLPA is similar to the PLPA except that the FLPA area is not pageable. Because its pages cannot be paged out or stolen, FLPA modules are always immediately available.
Unlike those in PLPA, modules that are loaded into FLPA and MLPA can come not only from the LPA libraries, but also from SYS1.SVCLIB and any of the linklist libraries. MLPA and FLPA modules must be reentrant by default. To disable the reentrancy enforcement, you can specify the NOPROT option in the general parameter member that names the specific IEAFIXxx and IEALPAxx members (that define FLPA and MLPA respectively). All of this makes their control more difficult. However, both of these memory‑resident libraries are fairly small, and between the two of them, rarely contain more than a few dozen modules.
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