SYS1.PROCLIB contains the JES2 cataloged procedure. This procedure defines the job-related procedure libraries. Figure 1 is an example of defining procedure libraries. All the libraries reside in the system's master catalog (or in a user catalog, provided the data set has a high-level qualifier other than SYS1).

//PROC00    DD    DSN=SYS1.PROC1,DISP=SHR
//PROC01    DD    DSN=SYS1.PROC2,DISP=SHR
...
//PROCnn    DD    DSN=SYS1.LASTPROC,DISP=SHR
//anyname   DD

The procedure library a job uses depends on the value of the PROCLIB= parameter on the JOBCLASS(v) initialization statement. Programmers can override the default specification by specifying a /*JOBPARM PROCLIB= statement in their JCL, and coding the name of the DD statement in the JES2 procedure that points to the library they want to use. For example, a programmer is running a job in class A. That class has a default PROCLIB of SYS1.PROC1. The programmer wants to use a procedure that resides in SYS1.LASTPROC. That programmer would include a /*JOBPARM PROCLIB=PROCnn in the JCL.

Another way to specify a procedure library is to use the JCLLIB JCL statement. See z/OS MVS JCL Reference for more information on the JCLLIB statement.

Any library that you will specify in initialization statements must have a name in the PROCnn form in the JES2 procedure or PROCLIB statements defining the logical PROCLIB. Other procedure libraries might have any DD name that follow the general rules for DD statements. If you require multiple data sets for one DD name, specify those data sets as concatenations in the JES2 cataloged procedure.

If the procedure library is not specified or specified and not found, PROC00 is used.