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mubs55
New User
Joined: 19 Apr 2006
Posts: 12
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Hi,
Can anyone let me know what might be the reason behind the Elapsed time being greater than CPU time.
One reason i know could be due to database problem. I would like to if it could result from other problems.
Regards,
Mubeena |
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UmeySan
Active Member
Joined: 22 Aug 2006
Posts: 771
Location: Germany
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Hi !
Normaly, in the step accounting data, the elapsed (wall clock) time for a job step represents the period between the beginning of the actual execution of the job step and the completion of all termination processing for it. Elapsed time is influenced by all I/O-activities. In BatchJobs using
large seq. datasets or VSAM you could reduce elapsed time by adding BUFFERS to the Dataset. Please have a look at BUFNO & BUFFND/BUFFNI statements in JCL.
Regards, UmeySan |
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DavidatK
Active Member
Joined: 22 Nov 2005
Posts: 700
Location: Troy, Michigan USA
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Mubeena,
Unless you are running dedicated on the processor, which is seldom if ever, the elapsed time will always be greater than the CPU time.
As ?UmeySan? said, elapsed time is from the start of your job/program to the end (Clock time)
CPU time, on the other hand, is allocated and accumulated by your job/program only when it is actually executing instructions. So, if there are 5 other jobs/programs vying for time on the processor, the CPU time must be shared between the other jobs/programs.
Depending on the priority you job is running in you may get more, or less of the shared CPU time than the other jobs running. |
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sundar28
New User
Joined: 30 Jul 2005
Posts: 11
Location: Mysore
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Hi Mubeena,
Elapsed Time = Time taken by the JES to submit and re-submit the job till its completion
+ CPU time
+ Time taken on waiting for the allotment of resources*
+ Time taken for response of the resources
( + User response time for interactive processes)
*resources - Files, Memory and Printers (and CICS or DB2 or MVS system call services like DATE, TIME etc)
Elapsed time can never be equal to the CPU time for an application program.
Please correct me if wrong. |
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sundar28
New User
Joined: 30 Jul 2005
Posts: 11
Location: Mysore
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| mubs55 wrote: |
One reason i know could be due to database problem.
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 Yes.
On tuning the database to optimize for the minimal response time, the time difference can be minimized. |
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mmwife
Super Moderator
Joined: 30 May 2003
Posts: 1592
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You forgot my favorite:
1) Your pgm calls for a tape to be mounted.
2) The tape pool operator decides to go to lunch.  |
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