Question: What is the difference between steplib,joblib,jcllib and when and where should each be used?
Answer: The joblib and steplib dd statements are used to specify alternate libraries where programs can be loaded from.
jcllib and proclib are used to specify where jcl is to be loaded from rather than programs. jcllib is used with the INCLUDE MEMBER statement to specify the library where pieces of jcl are held that can be included into a number of jobs. I have not seen this actually used, more often rather than separating out parts of job steps and including them it is more usual to extract out complete job steps into separate procedures stored in a proc library. proclib is the dd statement to override where to get procedures from.
This article written by Stephen Chapman, Felgall Pty Ltd.