The job entry subsystem (JES)

For useful work to be performed on z/OS®, SYS1.PROCLIB must contain a job procedure for the primary job entry subsystem.

To initialize JES, the master scheduler subsystem looks in SYS1.PROCLIB for the JES cataloged procedure. This procedure defines the job-related procedure libraries, including those that the JES subsystem uses to locate the JES initialization statements. A sample job procedure library is shown in Figure 1.

Figure 1. Job procedure libraries in the JES2 procedure

 //PROC00 DD  DSN=SYS1.PROCLIB,DISP=SHR
 //       DD  DSN=SYS3.PROD.PROCLIB,DISP=SHR
 //PROC01 DD  DSN=SYS1.PROC2,DISP=SHR
 ...
 //PROC99 DD  DSN=SYS1.LASTPROC,DISP=SHR
 ...

Many installations have very long lists of procedure libraries in the JES procedure. Care should be taken as to the number of users who can delete these libraries because JES will not start if one is missing. Normally a library that is in use cannot be deleted, but JES does not hold these libraries although it uses them all the time.

You can override the default specification by specifying this statement: /*JOBPARM PROCLIB=

After the name of the procedure library, you code the name of the DD statement in the JES2 procedure that points to the library to be used. For example, in Figure 1, assume that you run a job in class A and that class has a default PROCLIB specification on PROC00. If you want to use a procedure that resides in SYS1.LASTPROC, you'll need to include this statement in the JCL:/*JOBPARM PROCLIB=PROC99

Another way to specify a procedure library is to use the JCLLIB JCL statement. This statement allows you to code and use procedures without using system procedure libraries. The system searches the libraries in the order in which you specify them on the JCLLIB statement, prior to searching any unspecified default system procedure libraries.

Figure 2 shows the use of the JCLLIB statement.

Figure 2. Sample JCLLIB statement

 //MYJOB  JOB
 //MYLIBS JCLLIB ORDER=(MY.PROCLIB.JCL,SECOND.PROCLIB.JCL)
 //S1     EXEC PROC=MYPROC1
 ...

Assuming that the system default procedure library includes SYS1.PROCLIB only, the system searches the libraries for procedure MYPROC1 in the following order:

MY.PROCLIB.JCL
SECOND.PROCLIB.JCL
SYS1.PROCLIB