RE: SQL Optimizer Not Using Access Path

Kent,

The debug messages should have a description of the access path it created on the fly. How is that path different than the access path you created?

Paul Morgan

Principal Programmer Analyst
IT Supply Chain/Replenishment

-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Hohlen, Kent
Sent: Wednesday, April 06, 2011 3:12 PM
To: rpg400-l@xxxxxxxxxxxx
Subject: SQL Optimizer Not Using Access Path

I wrote an interactive RPG program using embedded SQL to retrieve
records from a rather large file (3 million records). It was performing
poorly and I noticed that there wasn't an access path that matched how I
was ordering the records. I created the access path and the performance
was still poor. I started debug and when I look at the debug messages
in the job log, the optimizer decided not to use the access path because
the cost to use this path was higher then creating a path on the fly. I
don't understand this. The access path keys match the order by fields.


I ran the same SQL statement in STRSQL and when I look at the debug
messages, this used the access path. I started the SQL Performance
Monitor and I saw a lot of information, but nothing that stated the
reason why this path was ignored.

Does anyone have any suggestions why this is might happen or any
suggestions on what to try?

We are running 5.4 with fixes current as of a few months ago.

Thanks,
Kent