(TPFUG/Visa) Need to remediate the overhead of special linkage libraries being in loadsets

Frequently Entered Program (FEP) support provides the means to alleviate the cost of having a program in a loadset that is entered many times by the same ECB. The FEP support allows an ECB to determine the version it should use by locking the base PAT slot to chase down the PATOLD chain ONCE, and then using the result on subsequent enters by that ECB.  The FEP support, however, does not support special linkage libraries : CISO, CTAL, CTIS, CTAD, CTDF.   

This means that loading a special linkage library in a loadset, e.g. as part of an APAR install, can result in an unacceptably large CPU increase. The CPU increase is made worse by more i/streams and at high system utilization. With the introduction of Low Priority workload whose purpose is to consume highly perishable, unused CPU cycles without impacting transactions, it is possible that a system is run at mid to high 90s CPU. In this situation, having a special linkage library in a loadset will drive up CPU, reducing the amount of CPU available to LP workload and therefore extending LP workload runtimes.  Although LP workload is low priority, it is likely that LP utilities have been tuned to ensure runtimes meet any required SLAs. Consequently,  significant increases in runtime can impact SLAs as well.

We need a way to remediate the cost of having special linkage libraries in an active loadset. The only other alternative is to procedurally ensure they are only loaded in a TLD and that could severely limit a customer's ability to install APARs, including critical APARs, quickly because they would have to schedule downtime.