Re: native i/o and RCAC - performance

Jay, that command to remove any cached file stuff is CLRPOOL - check out the help on it, not MUCH there, so maybe look online - for testing you want to control what all is happening, so isolating activity to a certain pool can give you apples=to=apples results better than doing something on an active production system.

There's another command, SETOBJACC, that can preload resources, like files, and can make for better performance - again, managing pools is a part of that exercise, otherwise what you preload might get paged out.

Good luck!
Vern

On 5/13/2021 8:10 AM, Jay Vaughn wrote:

thanks for that input Vern... it has to be something of that nature.
maybe some kind of built in deterministic behavior

Jay

On Thu, May 13, 2021 at 9:06 AM Vern Hamberg <vhamberg@xxxxxxxxxxxxxxx>
wrote:

Hi Jay

One theory - RCAC is a filter and might result in less I/O, depending on
the access plan - it is, I believe, using WHERE-clause kind of
filtering, if I heard things right a while ago. Of course, some of the
table might be resident in memory after the first loop, a fair test
normally needs to clear that - there's a command, something about
access, that I don't have on the tip of my brain right now.

Interesting finding, though!

Vern

On 5/13/2021 7:55 AM, Jay Vaughn wrote:

Can anyone explain or even theorize when applying RCAC to a file, how it
boosts the read performance of the file under native i/o?

Example:

file containing 5M rows...
simple RPG pgm in for loop with reads...

without RCAC applied
elapsed time - 23s
processing time - 1.544

with RCAC applied (alter table theTable activate column access control)
elapsed time - 4s
processing time - 1.413

drastic change in elapsed time - small change in processing time.

There is also a smaller gain when using SQL but not as much as native

i/o.

tia

Jay

--
This is the RPG programming on IBM i (RPG400-L) mailing list
To post a message email: RPG400-L@xxxxxxxxxxxxxxxxxx
To subscribe, unsubscribe, or change list options,
visit: https://lists.midrange.com/mailman/listinfo/rpg400-l
or email: RPG400-L-request@xxxxxxxxxxxxxxxxxx
Before posting, please take a moment to review the archives
at https://archive.midrange.com/rpg400-l.

Please contact support@xxxxxxxxxxxxxxxxxxxx for any subscription related
questions.

Help support midrange.com by shopping at amazon.com with our affiliate
link: https://amazon.midrange.com