Re: native i/o and RCAC - performance

I think Dr. Frank's concept of single-level storage is that memory and disk
are one big extent as far as the OS is concerned. So, the data in question
could be in physical memory, paged out, or not yet paged in.

CARPOOL: that's one I missed--thanks Vern!

On Thu, May 13, 2021 at 5:06 PM Vern Hamberg <vhamberg@xxxxxxxxxxxxxxx>
wrote:

Hi Leo

I don't think that's exactly how it works. SLS is a single address
space. There is also memory, and currently-in-use data sits there, too,
and that data is most-readily available to applications. But that is
limited in size, so data can be paged out of that area - until requested
again, then some other data will be paged out.

Using the SETOBJACC command, one can preload memory, let's say - this is
best used if you have a lot of memory and you load into a pool that is
not used for program activity. And CLRPOOL can page out everything from
a file that is in a pool, hence giving you a consistent base point for
performance testing.

Are the deer's eyes in the headlights yet? :)

Regards
Vern

On 5/13/2021 6:32 PM, Leo Burkett wrote:

How is a file pulled off hard disk and placed somewhere in single-level
storage? I thought single-level storage referred to a single address

space

spanning both RAM and disk.

Rob Berendt, you are a bad influence on me.

Leo Burkett

-----Original Message-----
From: RPG400-L On Behalf Of x y
Sent: Thursday, May 13, 2021 7:26 PM
To: RPG programming on IBM i <rpg400-l@xxxxxxxxxxxxxxxxxx>
Subject: Re: native i/o and RCAC - performance

Lots of reasons performance could be different, not the least of which is
the possibility that the file's been pulled off disk hard disk and is
sitting somewhere in single-level storage. I'd run this test at least 10
times in succession, alternating with/without RCAC, to tamp down system
workload and the other unseen factors that play havoc with performance
measurement. My development partition has 245 jobs running--a handful of
QINTER's, one user daemon, and a handful of

It seems that this feature is extremely useful in some very specific use
cases, primarily to protect financial and employee-confidential data, but
not the most effective for dealing with performance issues. Another

approach

is to create a covered index/access path, where all the fields/columns
needed for a given query are included in the "logical".

On Thu, May 13, 2021 at 5:57 AM Jay Vaughn <jeffersonvaughn@xxxxxxxxx>
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
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