Chapter 7. Systems management 137
7.5.1 Batch scheduling
A major task facing large-scale commercial operating systems is dealing with a
huge number of batch jobs. Having thousands of batch jobs a day is quite normal
for a medium to large sysplex system, and it usually represents between 50%
and 70% of the total work. The heavy contribution of batch jobs to the overall
system workload is what drove the development of tools to automate the
scheduling and execution control of batch jobs.
The z/OS implementation of such tools range from a relatively simple solution
based on direct relations and deadlines implemented by the Job Entry
Subsystem (JES2 or JES3), to more sophisticated tools that specialized vendors
(including IBM) have developed.