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Another mechanism that manages data on the system concerns the programs that are stored in load libraries and their directories. Program libraries can contain programs that z/OS cannot run. When the linkage editor processes a program to convert it from object modules to a loadable format, certain errors can occur that keep it from running. The linkage editor puts the machine language program in the program library anyway, but marks it with a flag that tells z/OS not to run it.
It is easy for programmers to miss the messages that tell them that a program is not executable. If proper testing and change control procedures are in effect at the data center, this type of situation should be detected before a program is put into production. However, it is possible that the programmer discovers the problem only when the production job stream that was supposed to run his program abends in the middle of the night.
Load libraries can be damaged through hardware errors or through improper sharing of libraries. Many people simultaneously trying to update a load library without using standard procedures can easily damage a load library. The directory of the library gets tangled, and when z/OS tries to load a program, it gets garbage instead.
It is also possible that a load library can “bury” procedure library (proclib) members. Any PDS, even load libraries, can be proclibs. If you detect any errors in a load library, it would be wise to use the JES2 Proclib Display (4.2) to see if that load library is shown as a potential proclib. See the description in the chapter “Program Information” for more information about proclibs. The Program Library Analysis function (6.1.2) analyzes the load libraries on the system. It reads through the directory of a library and attempts to load each program, just as z/OS would if the program were running. If any programs fail to load, CA Auditor tells you which ones did not load. Otherwise, it indicates that no load library errors are found.
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