Re: Query; Forcing Queries to use exsisting Access Paths

[Pete Hall <peteh@xxxxxxxxxx>]

At 20:06 01/03/1999 -0800, Karen Burke wrote: 

> I heard someone
> mention an AS400 Query guru. They talked about forcing queries to use
> exsisting access paths, how do you do this? We run 25 queries daily to
> build a data file for our users to query at my company--this takes 3 to 4
> hours to run and if possible ofcourse we would like to save time. I took
> out all sort references like recommended and didn't seem to gain much
> time. We are running V4 R1.

I'm no guru, but I've played with this stuff quite a bit lately. Turn on
debug and watch the joblog. The query optimizer will log messages that
will tell you what you need to do to create an appropriate access path,
if that's the problem. Quite honestly though, lately (V4R2 at the
moment), creating access paths hasn't been the problem. It has been
making copies of files or using arrival sequence to select records from
files with several million records in them. Watch what the job is doing
that takes so long. If it's either of the above, you may be able to
improve it dramatically by separating it into smaller discrete steps that
produce intermediate result files, and them combining those into the
final output with a join.

Pete Hall

peteh@inwave.com

http://www.inwave.com/~peteh