RE: Different processing times...why?

["Andy Nolen-Parkhouse" <aparkhouse@xxxxxxxxx>]

Ray,

Here's a possible explanation.  Whether it's accurate or not would
depend on how busy your system is and how much main storage you have in
the pool in which your job is running.

When any program reads data from a file, it must bring the data into
main storage.  Generally speaking, this data will stay in memory until
the system needs to use that memory for something else.  On the first
pass through the program, probably all data needs to be brought into
main storage by going to the disk and doing a lot of reads.  These disk
reads will take a fair amount of time.

Depending on available main storage, a large amount of this data could
still be in memory when you run it the second time, so most "disk
accesses" will actually occur in memory, leading to considerably shorter
processing times.

Regards,
Andy

> On Behalf Of Ray Nainy
> Subject: Different processing times...why?
>
> We have an RPG program that reads approximately 4500 records from
> file A and reads matching records in file B using account number.
> File B has a total of 2 million records.
> It takes about 60 to 70 seconds to complete the processing when the
> program
> is called for the first time. But it takes only 3 to 4 seconds to
complete
> the processing, when the program is called again 2nd or 3rd or 4th or
> 5th...time. Processing time is 60 to 70 seconds only for the first
call.
> This happens again if the session is idle for 20 minutes or more. We
> couldn't find out why is this processing time more only for the first
call
> to the RPG program. We verified and found that this problem exist
> anytime, irrespective of the peak/non-peak hours of the day.
>
> Any help is greatly appreciated.
>
> Ray