jcl

Can anyone tell the difference between joblib, steplib and jcllib?

JCLLIB - Denotes the location of JCL fragments pulled in by INCLUDE statements.

STEPLIB - Denotes a load lib that is searched first when trying to determine the location of a load module.

JOBLIB - Same as STEPLIB but on a job level

Note - In practical use, JOBLIB is used by lazy coders who end up concatenating every possible loadlib. This causes every program call in that job to search the JOBLIB dd. In turn, this adds overhead to each step, particularly when the load module is not in the JOBLIB sequence.
In other words, avoid JOBLIB and only code STEPLIB when absolutely necessary.