RE: program/file data structure

>Date: Mon, 6 Dec 1999 19:28:09 -0600
>From: "Joe Teff" <jteff19@idt.net>
>
>This post was from a while back
>
> >Warning: Filling up the entire PSDS can be costly at
> >initialization time - some of the information is costly
> >to calculate. If you don't need all of the fields at
> >the end of the DS, it might be a good idea to have some
> >smaller versions of the PSDS (maybe using logical files?).
> >Barbara Morris
>
>Could you please identify exactly which fields you are referring to.
>...

The fields that cost non-trivial amounts to calculate are
- the program library (pos 81-90)
- Date job started (pos 191-198 and also used in later positions)
- Job name/user/number (pos 244 - 269)
- Job date (pos 276-293)
- Start time (pos 282-287)
- Program (pos 334-343)
- Module (pos 344-353)
- Current user profile (pos 358-367)

The compiler doesn't care if you have defined subfields for any of
these - it decides whether to fetch the information based on the
length of the PSDS.

Some figures:
Calling a program with a full-length PSDS and one with no PSDS
(just doing a seton LR) 100,000 times:
- with full PSDS: 21 seconds
- with no PSDS: 4 seconds

But please don't worry too much about this.  This difference is
somewhat spectacular, but it's basically insignificant since the time
taken to do 100,000 calls is "fast enough".  It's just one consideration
-if- you have a performance-sensitive program that ends with LR on, and
-if- you don't need some of the expensive fields in the PSDS.

This applies to the ILE RPG compiler only.  The RPG/400 (RPG III)
compiler always does the whole PSDS.

Barbara Morris


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