1.What is the difference between JCL and JES.?
2.What is the difference between VSAM and DB2?

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  • Jan 19th, 2012

JCL is a language,
We write JOBs in JCL laguage that is understood by Mainframe and job is executed, space allocations & other resource allocation is done according to the keywords specified by you in JCL.

JES is the MVS subsystem(part of your mainframe) that will handle/process/Schedule/allocates the JOBS/JCLs submitted by users

In short once you submit your JCL, JES will takes control of it, it will generates an JOB iD, validates your JCL for syntax errors , Shedule your job for execution, Allocates virtual memory for execution, allocates datasets specified iDD statementys etc ..... after completion of the execution it will deallocates the virtual memory of your JCL and finally purges the job from system

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