interpertting a db2expln

[Database Administrator]

Hey Serge,

Is there actually somewhere a good document describing the explain plan and
what each section means etc..?
For example, MAXPAGES. From what I understand so far is the optimizer
setting the maximum number of pages to prefetch correct?
But I've seen a setting of like 1000, so that would mean to maximum fetch
1000 pages correct?
Thus if I have a prefetchsize of 32, I would get 32 prefetch requests
correct?

So if it would for example say 16, would this mean that although my
prefetchsize if set to 32, the optimizer will override this and only get 16
pages?

I can not find any good documentation explaining every item within the
explain output, and what it means etc..

Thanks.

"Serge Rielau" wrote in message
news:c1lhar$hmk$1@hanover.torolab.ibm.com...
> Feed the query into
> db2 EXPLAIN PLAN FOR
> then do:
> db2exfmt
>
> The result will be a lot more verbose.
> db2expln reverse engineers (disassembles) the plan from the runtime.
>
> E.g. db2exfmt will tell you the estimated (or proven) cardinality of
> each plan operator.
> In your case I would expect a "truncated sort".
> Cheers
> Serge
> --
> Serge Rielau
> DB2 SQL Compiler Development
> IBM Toronto Lab

[finditout]

Also one more question related to the same.
From where db2expln takes "Isolation value"? as I tried changing isolation level to RR ( on session level) still db2expln showing me the default one (CS).