In this topic, we described about the Class with detailed example.
CLASS parameters used to categorize the jobs. The categorization is either SHORT RUN jobs or LONG RUN jobs. CLASS parameter is an optional parameter. CLASS parameter is used to achieve good balance in the system. CLASS parameter is used to avoid the contention between the jobs which are using same resource. System operations department can help to determine which job classes are available for use.
|Job-class||Identifies the job class|
CLASS parameter value always referred with one letter.
CLASS parameter value allows alphabets (A-Z characters), numbers (0-9). In total 36 different values can be allowed as CLASS parameter value. CLASS parameter values predefined by system during system installation.
Every CLASS parameter value defined has its own characteristics. CLASS definition includes number of resource constraints, usage and CPU time etc. The same CLASS parameter value on different JOBs usually group the jobs based on the predefinition.
If job CLASS is not coded, system uses installation-defined standard default class.
A JES3 //*MAIN statement CLASS parameter overrides a JOB statement CLASS parameter.
Assume some system has defined a class parameter values are from A to Z where A is for shortest run jobs and Z is for long run jobs. JOB A is using B class parameter, JOB B using Z class parameter and JOB A, JOB B are using same other parameters.
What happened if both jobs are submitted at the same time?
JOB A executes first and JOB B executes next because of the class parameter definition.