I neglected to send up update last night.

I changed the program (rewrote it really) to use SQL to do the summing with
group by and eliminated the humungous arrays. It now runs consistently
under 5 minutes.

I leaning toward the arrays being the bigger culprit. After digging a
little deeper to understand the code, it was clearing the 22 arrays with
most being 15p4 and all dim at 32767 (totaling about 10,419,906 bytes)
almost 10,000 times. Some day I'm going to play with that concept and see
how much time that really takes. Meanwhile, I am in the testing/validation
stage.

Thanks everyone for your input. Even things that weren't applicable this
time will probably ring a bell down the road and help me solve a future
problem.



-----Original Message-----
From: RPG400-L <rpg400-l-bounces@xxxxxxxxxxxxxxxxxx> On Behalf Of D*B
Sent: Friday, October 16, 2020 4:19 AM
To: RPG programming on the IBM i / System i <rpg400-l@xxxxxxxxxxxxxxxxxx>
Subject: RE: Performance question of RPG native read vs SQL

<smith5646midrange>
Unfortunately, the entire driver file is needed to build the summary file.
The driver is a transaction based file. It is rolled up to the summary level
so they don't have to chug through the transactions every time. There is no
selection. Only a top to bottom keyed read.
</smith5646midrange>

... if you could bring it to a bulk statement like create table ... as
select ...
or
insert into ... select ...

this would beat the row by row processing, regardless wether you are using
RLA or SQL to do this.
even faster versions could be done with parallelism (if your ressources are
not constrained.

If your process is doing additional logic, first step would be to analyze
where thr most time in consumed.

D*B

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