Performance adjustment and query optimization

[Rob Berendt <rob@xxxxxxxxx>]

I believe I've read somewhere that having automatic performance adjustment 
on can have an adverse effect on query optimization.  Because when the 
query optimizer runs it ignores the previous optimization analysis and 
reanalyzes if the memory changes because the memory available is taken 
into the calculation.  So, if you have like a million sql statements in a 
loop (canned vendor package) each time it loops it may have to reanalyze 
because the memory changes, well maybe not every loop because the adjuster 
is not quite that fast to recalculate.

I have a PMR open with IBM and they are looking at Job Watcher data and 
now have moved on into SQL plan cache but while waiting on that I wanted 
to explore other things.

Also, on a closely related note, does having your paging set *CALC vs 
*FIXED affect query optimization?
See WRKSYSSTS and WRKSHRPOOL 


Rob Berendt