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  3. December 2010

RE: Processing Unit Time

SELECT SUM ( CASE : H WHEN 'DR' THEN ECDEAM ELSE ECDQTY END )
INTO : H
FROM IMSPRECH
JOIN IMSPRECD
ON ECDCONO = ECHCONO
AND ECDSTR = ECHSTR
AND ECDRCT = ECHRCT
AND ECHCONO = : H
AND ECHDTE BETWEEN : H AND : H
AND ECDCONO = : H
AND ECOVND = : H
AND ECDEXT = : H

Will look for three indexes. One for the join, one for table 1 (IMSPRECH) record selection and another for table 2 (IMSPRECD) record selection.

If I were to change the statement to...
SELECT SUM ( CASE : H WHEN 'DR' THEN ECDEAM ELSE ECDQTY END )
INTO : H
FROM IMSPRECH
JOIN IMSPRECD
ON ECDCONO = ECHCONO
AND ECDSTR = ECHSTR
AND ECDRCT = ECHRCT
AND ECHCONO = : H
AND ECHDTE BETWEEN : H AND : H
-- AND ECDCONO = : H
AND ECOVND = : H
AND ECDEXT = : H

I've commented out the ECDCONO because of the join. But it will still try to find an index for table 2 (IMSPRECD) by ECOVND and ECDEXT. It will not find one so it will end up doing a table scan on table two before doing the join ever occurs.

Like you said you could get away with this if I keep the record selection on the where clause as the where clause does the selection after the join.


-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Luis Rodriguez
Sent: Tuesday, December 21, 2010 3:08 PM
To: Midrange Systems Technical Discussion
Subject: Re: Processing Unit Time

Just wondering, if the WHERE clause is done AFTER the JOIN, would it matter
if you specify ECHCONO and ECDCONO again? (assuming you change your JOIN
clause to use ECHCONO = : H)

Regards,

Luis Rodriguez
IBM Certified Systems Expert - eServer i5 iSeries
--



On Tue, Dec 21, 2010 at 3:27 PM, Schutte, Michael D <
Michael_Schutte@xxxxxxxxxxxx> wrote:

ECHCONO = :H and ECDCONO = :H may be redundant, however, I don't have
indexes by ECOVND and ECDEXT. So in order to take advantage of the ECDCONO,
ECOVND, ECDEXT index, I need to select on all three fields.

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:
midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Luis Rodriguez
Sent: Tuesday, December 21, 2010 2:21 PM
To: Midrange Systems Technical Discussion
Subject: Re: Processing Unit Time

Michael,



(Just curious) In your statement:



SELECT SUM ( CASE : H WHEN 'DR' THEN ECDEAM ELSE ECDQTY END )

INTO : H

FROM IMSPRECH

JOIN IMSPRECD

ON ECDCONO = ECHCONO

AND ECDSTR = ECHSTR

AND ECDRCT = ECHRCT

WHERE ECHCONO = : H

AND ECHDTE BETWEEN : H AND : H

AND ECDCONO = : H

AND ECOVND = : H

AND ECDEXT = : H



Am I right in supposing that ECHCONO, ECHSTR and ECHRCT belong to
IMSPRECH?
Most of the time I see the join fields in the same order as the tables are
expressed, e.g. ECHCONO = ECDCONO (just a personal question of style, I
realize, nevertheless, curious all the same :-) ).



Also, IIRC, the WHERE clause works AFTER the tables have been joined, so
what happens if you change your first join clause to ECHCONO = : H , which
would limit the size of your JOIN file and drop the ECHCONO = : H
andECDCONO = : H clauses
(which, if I'm not mistaken, are redundant anyway, as they are part of the
JOIN clause). Run that again thru VE and see if it suggest a different
index.



Regards,
Luis Rodriguez
IBM Certified Systems Expert - eServer i5 iSeries
--



On Tue, Dec 21, 2010 at 1:20 PM, Schutte, Michael D <
Michael_Schutte@xxxxxxxxxxxx> wrote:

Yes I have thought about it. Unfortunately that requires time to redo
the
program. I even suggested to my boss, but he's leaning toward moving to
a
different job queue. I'm just not understanding the 1448 seconds of CPU
time. What isn't being accounted for in this measurement? I know that
it
says nine seconds. But really doesn't. If you run interactively, it's
like
12ms. Anyway, thanks for the input. When I have time, I'll redesign by
summarizing the table first and querying the summary table.

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:
midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Morgan, Paul
Sent: Tuesday, December 21, 2010 11:50 AM
To: Midrange Systems Technical Discussion
Subject: RE: Processing Unit Time

Mike,

240,000 runs times the estimated query run time of 9 seconds is 2,160,000
seconds = 600 hours. Not bad that it finished in 11 hours.

Have you thought about modifying the query so it's only executed once to
a
work table for all retail items (maybe linking to another table with the
retail items) and summarizing for each month of the past twelve months?
Then you run through the work table to make your calls to
updHTMLvar/WrtSection.

Paul Morgan

Principal Programmer Analyst
IS Supply Chain/Replenishment


-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:
midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Schutte, Michael D
Sent: Tuesday, December 21, 2010 11:15 AM
To: Midrange Systems Technical Discussion
Subject: RE: Processing Unit Time

No the access plan isn't getting updated on each call. It was last saved
at 10:28:05 That's when the program started, it finished at 21:34. I
suppose I cannot count. It only took 11 hours not 12. Haha. I believe
yesterday this sql statement was executed for every active retail item
(20,000 items) and for the past 12 months. So 20,000 * 12 = 240,000
times
the statement ran. After every call to sql statement, I'm executing
updHTMLvar and WrtSection. I know that this would slow the process
overall.

Thinking back, this was probably poor design, but it wasn't really
intended
to run for all items and all vendors, even though the prompt program
allows
the user to do so. But still, I can live with CPU time of 1448 seconds,
cannot live with 11 hours of actual run time. This is what I don't
understand.


-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:
midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Morgan, Paul
Sent: Tuesday, December 21, 2010 10:31 AM
To: Midrange Systems Technical Discussion
Subject: RE: Processing Unit Time

Michael,

How many times does this get run in the process? You're talking about
repeated calls to CGIDEV2 so does this get run once for each call? Is
the
access plan getting updated on each call?

Paul

Principal Programmer Analyst
IS Supply Chain/Replenishment


-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:
midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Schutte, Michael D
Sent: Tuesday, December 21, 2010 10:10 AM
To: Midrange Systems Technical Discussion
Subject: RE: Processing Unit Time

This is from the PRTSLQINF command.

SELECT SUM ( CASE : H WHEN 'DR' THEN ECDEAM ELSE ECDQTY END )
INTO : H
FROM IMSPRECH
JOIN IMSPRECD
ON ECDCONO = ECHCONO
AND ECDSTR = ECHSTR
AND ECDRCT = ECHRCT
WHERE ECHCONO = : H
AND ECHDTE BETWEEN : H AND : H
AND ECDCONO = : H
AND ECOVND = : H
AND ECDEXT = : H

SQL4021 Access plan last saved on 12/20/10 at 10:28:05.
SQL4020 Estimated query run time is 9 seconds.
SQL4017 Host variables implemented as reusable ODP.
SQL4007 Query implementation for join position 1 table 2.
SQL4006 All indexes considered for table 2.
SQL4008 Index IMSLRECD9 used for table 2.
SQL4011 Index scan-key row positioning used on table 2.
SQL4007 Query implementation for join position 2 table 1.
SQL4006 All indexes considered for table 1.
SQL4008 Index IMSLRECH1 used for table 1.
SQL4014 1 join column pair(s) are used for this join position.
SQL4015 From-column 2.ECDCONO, to-column 1.ECHCONO, join operator MF,
join predicate 1.
SQL4015 From-column 2.ECDSTR, to-column 1.ECHSTR, join operator MF,
join
predicate 2.
SQL4015 From-column 2.ECDRCT, to-column 1.ECHRCT, join operator MF,
join
predicate 3.
SQL4011 Index scan-key row positioning used on table 1.

If it was doing a table scan, the print out above would show it and
wouldn't the CPU time be a lot greater. FYI, we didn't have any other
jobs
running on the system with higher priority. CPU% was around 70%. I don't
know. I'm starting to believe that it had nothing to do with the
statement
itself but rather the repeated calls to WrtSection of the Dev2
procedures.

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:
midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Morgan, Paul
Sent: Tuesday, December 21, 2010 9:37 AM
To: Midrange Systems Technical Discussion
Subject: RE: Processing Unit Time

Michael,

Try running the process under debug (STRDBG/ENDDBG). That will get the
SQL
access plan printed in the job log. You can then review the access plan
to
see if it's actually using the logicals. Sometimes SQL will reject a
logical for a sequential access if the previous run was very fast. It
thinks a sequential read through the file will be faster than including
the
overhead of an indexed read.

Paul Morgan

Principal Programmer Analyst
IS Supply Chain/Replenishment

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:
midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Schutte, Michael D
Sent: Tuesday, December 21, 2010 8:37 AM
To: Midrange Systems Technical Discussion
Subject: Processing Unit Time

I'm having trouble finding an explanation of this but I was wondering if
someone could explain this here. A user submitted a job the other day
that
took 6 hours to complete. By looking at the SQL statement in the
program, I
saw where an improvement could be made. I created a new logical by the
selection keys in the where clause, so now the statement take less than a
second to run for a month of data and the entire company. The user
resubmitted the job yesterday and this time it took 12 hours to complete
while using the new logical. If you look at the job log it says that it
only used 1448 seconds processing unit time. That's only 24 minutes.
So
why did it take 12 hours. Is it because it created a 23,000 page job
log?

There are two messages that are repeated over and over again that I can
fix. Dataarea CGIDEBUG not found and null indicator require. The reason
for the CGIDEBUG message is because I'm using the CGIDEV2 procedures to
build an HTML page and then use write to stream file function so that I
can
email it to the user. Then for the null indicator, the sql statement is
summing a field but I'm not checking any statuses nor using a null
indicator. I've always just set the INTO field to zero prior to
executing
the statement. I should change my habit to always use a null indicator
so
that this message isn't created in the job log. But I don't see why this
would cause the program to run for 12 hours.

Any thoughts?


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