Paul:
I've pointed this out several times over the last couple of months.
Auto tune by definition changes the storage available and activity levels in
shared memory pools. That's what it does.
Whenever an SQL statement is run the first thing the optimizer does is check
to see if the environment changed. If no changes (memory size etc. ) then
run the query. If any changes, then reoptimize the query and run it.
One a lighter loaded system, you most likely will not notice a difference
since query optimization is fairly fast, but on a heavily loaded system it
can make a big difference. Furthermore, since conditions change with auto
tune a query might run using indexes, hash look ups, and index look ups one
time, then the next time table scan several large tables since the cost to
build the index might be higher than the table scan. It all depends on the
environment. You'll be asking the list why that might happen since unless
you really pay attention to the plan cache, you won't see why the optimizer
does what it does.
Solution: for those pools where SQL is running do not change them. Hence,
auto tune in any variety is ruled out.
--
Jim Oberholtzer
Agile Technology Architects
-----Original Message-----
From: MIDRANGE-L <midrange-l-bounces@xxxxxxxxxxxx> On Behalf Of Steinmetz,
Paul
Sent: Monday, December 03, 2018 10:19 AM
To: 'Midrange Systems Technical Discussion' <midrange-l@xxxxxxxxxxxx>
Subject: RE: DB2 Symmetric Multiprocessing (option 26 of 5770SS1) Was:
Performance tuning
Jim,
< (no autotune !!!!)
Why
Paul
-----Original Message-----
From: MIDRANGE-L [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Jim
Oberholtzer
Sent: Monday, December 03, 2018 10:07 AM
To: 'Midrange Systems Technical Discussion'
Subject: RE: DB2 Symmetric Multiprocessing (option 26 of 5770SS1) Was:
Performance tuning
Rob:
Clearly that LPP only helps with SQL, not so much Record Level Access.
Secondly proper indexing etc. must be done. Most critically however is the
partition needs to have more than one core assigned to it.
System values need to be set to enable it (QQRYDEGREE for example)
The query attributes need to be set to use it, be they set from the QAQQINI,
"Set current Degree" or other methods.
Now index creation can now be parallel, query execution will be broken up
into parts
Furthermore, it's not a set and forget product. Periodically the query
attributes need to be reviewed, index creation reviewed, and more
importantly update the work management as needed. (no autotune !!!!)
You won't belielive how many systems I look at where that product is
installed and at least one of the above is not done.
--
Jim Oberholtzer
Agile Technology Architects
-----Original Message-----
From: MIDRANGE-L <midrange-l-bounces@xxxxxxxxxxxx> On Behalf Of Rob Berendt
Sent: Monday, December 03, 2018 8:21 AM
To: Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxx>
Subject: DB2 Symmetric Multiprocessing (option 26 of 5770SS1) Was:
Performance tuning
<snip>
We include it in most every upgrade if we can. The other one we like to
include is DB2 Symmetric Multiprocessing (option 26 of 5770SS1) when there
are more than two cores on the system. That's another LPP that really helps
when utilized properly.
</snip>
I'm interested in further comments about <snip> when utilized properly
</snip>
Rob Berendt
--
IBM Certified System Administrator - IBM i 6.1 Group Dekko Dept 1600 Mail
to: 2505 Dekko Drive
Garrett, IN 46738
Ship to: Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com
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