RE: Externalizing Data Access - Reducing Disk I/O

Whether in a subprocedure or a subroutine, if I anticipate the successive chains *may* occur (and I don't really need to get the same record again, I simply check the field(s) to use on the CHAIN to the previous CHAIN's key field(s). Naturally, you have to save the key field(s) and test, but that's considerably faster than a disk I/O.

Jerry C. Adams
IBM System i Programmer/Analyst
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B&W Wholesale
office: 615-995-7024
email: jerry@xxxxxxxxxxxxxxx


-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Johnson, Brian (EU)
Sent: Thursday, April 23, 2009 8:58 AM
To: rpg400-l@xxxxxxxxxxxx
Subject: Externalizing Data Access - Reducing Disk I/O

We're developing some RPG modules (bundled into a service program) that
have externalized access to some data files. Due to some of the data
layout, I have a concern of excessive data I/O.

We have a procedure that returns the size array attribute for an
article. The code itself works great. My concern is where we
repeatedly call the procedure with the same incoming parameter, and the
procedure constantly chains the same record over and over again. My
hope (and coding) was that the subprocedure retained knowledge of
existing record in memory, and prevent the additional chain, but that
doesn't appear to be the case.

Is there anything else I can do to reduce unneeded disk I/O?

Thanks,
Brian

Example:

(INVOKES EXPORTED PROCEDURE)
C eval TmpSizeA =
GetStyleSizeA(%subst(InArt:1:8))


****************************
* Procedure - GetStyleSizeA
****************************
* Returns Style Size Array Code

P GetStyleSizeA b export

* Input Parameters
D GetStyleSizeA pi 3
D InStyle 11 const

D OutMaat s 3

* Only chain record if not already active (Reduces Disk I/O)
C if arnrmb <> InStyle

C eval OutMaat = *Blanks
C InStyle chain(n) coarmbl0
C if %found(coarmbl0)
C eval OutMaat = maatmb
C endif

C endif

* Return size array code
C return OutMaat

P e



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