configuration advisor on buffer pool size

[xixi]

hi, we are using db2 udb v8.1 on windows, i try to use the
configuration advisor to get recommendation on the parameter setting,
at first, i give the target memory for DB2 is 80% of the physical
memory, it gives me a recommendation on bufferpool size, so i accept
the change, later on , i found that i gave too much memory to DB2, so
i change the target lower, but the recommendation doesn't change the
buffer pool size accordingly, why is that? thanks

[Pierre Saint-Jacques]

That the buffer pool value 4000000 (4M pages ???) does not change after
you new specs. has me confused.
Is it really 4,000,000 pages??? That really is 16 GB of memory and
you'd absolutely need t run on a 64 bit system for this.

If you set it at 4MB or 1000 pages then it should not change even if you
only claim 40% of memeory on the second run of your advisor.

Torestate, I do not think that the Advisor changes the 80% claim when it
starts for every time it runs. I do not think that there's a paramater
that will remeber you chose 60% one time, 40% another and so on. It
just comes up with 805 each time and lets you reset.
HTH, Pierre.

xixi wrote:

when i use the configuration advisor, the first screen come up with a
slide bar as target memory 80%, then i take it and finish the rest of
the steps, it gives me recommendation on the bufferpool size , e.g.
4000000 (about 2g) , so i accept it. later on the same server(windows
2003) has to hold app server and the database server at the same time,
and also i have two databases being used under same instance, so i
decided to use the configuration advisor change the target memory, the
first screen still come up with 80% target, i slide the bar to use
40%, finish the rest of steps, then i saw the recommendation for the
bufferpool size doen't change , still 4000000, that is why confusing
me. why the new update on the memory is not reflected?

--
Pierre Saint-Jacques - Reply to: sesconsjunk at attglobaljunk dot com
Reconstruct address: Remove the two junk and replace at and dot by
their symbols.
IBM DB2 Cerified Solutions Expert - Administration
SES Consultants Inc.

[xixi]

sorry , it should be 400,000 pages, we do run on a 64bit machine.

i change the memory slide bar to 40% of target, the new bufferpool
size doen't change for recommendation, no matter i start the DB2 or
not, i have to manually do the change for bufferpool size i guess. it
is inconvenient.

[xixi]

sorry , it should be 400,000 pages, we do run on a 64bit machine.

i change the memory slide bar to 40% of target, the new bufferpool
size doen't change for recommendation, no matter i start the DB2 or
not, i have to manually do the change for bufferpool size i guess. it
is inconvenient.

[Pierre Saint-Jacques]

Xixi, it is working as expected but not as you expect.
Changing the slider on the Advisor from 80% to 40% affects not only the
size of buffer pools.

What the % means is that you are reserving 40%(or 80%, 60%, ...) for all
of the DB Global Shared Memory.
This includes the DB Heap, Package Cache, Catalog Cache, Locklist,
SortHeapTrhresh old_Share, and so on.
So for a 400,000 pages buffer pool aggregate, you need a DB Heap of
about 16,000 pages. The rest should total 10,000 pages at the very most
which gives you a Global Shared Memory request of about 430,000 pages,
or a little over 1.75 GB for Global Shared Memory.
If you set aside 20% of memory for the OS and its Services plus the DAS
and the instance, and then 40% for Global Shared Memory, then the
leftover 40% will be used for the coordinator agents of your connections.

From prior docs. in tuning, a rough rule of thumb is to allocate 20%
for OS and stuff, then use 65% of leftover memory for buffer pools in an
OLTP system, Or, 50% for buffer pools in a DSS system, in this case the
last 10% should be given to the sortheaps.

HTH, Pierre.

xixi wrote:

sorry , it should be 400,000 pages, we do run on a 64bit machine.

i change the memory slide bar to 40% of target, the new bufferpool
size doen't change for recommendation, no matter i start the DB2 or
not, i have to manually do the change for bufferpool size i guess. it
is inconvenient.

--
Pierre Saint-Jacques - Reply to: sesconsjunk at attglobaljunk dot com
Reconstruct address: Remove the two junk and replace at and dot by
their symbols.
IBM DB2 Cerified Solutions Expert - Administration
SES Consultants Inc.

[Pierre Saint-Jacques]

Xixi, it is working as expected but not as you expect.
Changing the slider on the Advisor from 80% to 40% affects not only the
size of buffer pools.

What the % means is that you are reserving 40%(or 80%, 60%, ...) for all
of the DB Global Shared Memory.
This includes the DB Heap, Package Cache, Catalog Cache, Locklist,
SortHeapTrhresh old_Share, and so on.
So for a 400,000 pages buffer pool aggregate, you need a DB Heap of
about 16,000 pages. The rest should total 10,000 pages at the very most
which gives you a Global Shared Memory request of about 430,000 pages,
or a little over 1.75 GB for Global Shared Memory.
If you set aside 20% of memory for the OS and its Services plus the DAS
and the instance, and then 40% for Global Shared Memory, then the
leftover 40% will be used for the coordinator agents of your connections.

From prior docs. in tuning, a rough rule of thumb is to allocate 20%
for OS and stuff, then use 65% of leftover memory for buffer pools in an
OLTP system, Or, 50% for buffer pools in a DSS system, in this case the
last 10% should be given to the sortheaps.

HTH, Pierre.

xixi wrote:

sorry , it should be 400,000 pages, we do run on a 64bit machine.

i change the memory slide bar to 40% of target, the new bufferpool
size doen't change for recommendation, no matter i start the DB2 or
not, i have to manually do the change for bufferpool size i guess. it
is inconvenient.

--
Pierre Saint-Jacques - Reply to: sesconsjunk at attglobaljunk dot com
Reconstruct address: Remove the two junk and replace at and dot by
their symbols.
IBM DB2 Cerified Solutions Expert - Administration
SES Consultants Inc.

[xixi]

thanks for your quick reply to my email. i think what i try to say is
at the beginning, i want to give DB2 server 80% of memory (includes
you said global memory, db heap, .....), so it gives me
suggestion on the bufferpool size to 400000 pages, and some other
changes on locklist, package heap too, so i accept the changes, now
the bufferpool size is 400000 pages, but it gives me problem since i
have a application server hold on the same machine, i need to give it
memory too, so i decide i should let DB2 has only 40% of total memory,
give 40% memory to application server,
then i change only give DB2 to 40% of memory, but it gives me some
advice on logfilesize change, package cache size, but no advise on the
bufferpool size, so when i look at by control center, the size is
unchanged , i have to manually do it. shouldn't be advise change from
the advisor after i gives different memory request?

[xixi]

thanks for your quick reply to my email. i think what i try to say is
at the beginning, i want to give DB2 server 80% of memory (includes
you said global memory, db heap, .....), so it gives me
suggestion on the bufferpool size to 400000 pages, and some other
changes on locklist, package heap too, so i accept the changes, now
the bufferpool size is 400000 pages, but it gives me problem since i
have a application server hold on the same machine, i need to give it
memory too, so i decide i should let DB2 has only 40% of total memory,
give 40% memory to application server,
then i change only give DB2 to 40% of memory, but it gives me some
advice on logfilesize change, package cache size, but no advise on the
bufferpool size, so when i look at by control center, the size is
unchanged , i have to manually do it. shouldn't be advise change from
the advisor after i gives different memory request?

[Paul Vernon]

"xixi" <da****@yahoo.c om> wrote in message
news:c0******** *************** ***@posting.goo gle.com...

thanks for your quick reply to my email. i think what i try to say is
at the beginning, i want to give DB2 server 80% of memory (includes
you said global memory, db heap, .....), so it gives me
suggestion on the bufferpool size to 400000 pages, and some other
changes on locklist, package heap too, so i accept the changes, now
the bufferpool size is 400000 pages, but it gives me problem since i
have a application server hold on the same machine, i need to give it
memory too, so i decide i should let DB2 has only 40% of total memory,
give 40% memory to application server,
then i change only give DB2 to 40% of memory, but it gives me some
advice on logfilesize change, package cache size, but no advise on the
bufferpool size, so when i look at by control center, the size is
unchanged , i have to manually do it. shouldn't be advise change from
the advisor after i gives different memory request?

Does the DB2 command
AUTOCONFIGURE USING mem_percent 40 APPLY NONE
suggest different sizes?

Regards
Paul Vernon
Business Intelligence, IBM Global Services

[Paul Vernon]

"xixi" <da****@yahoo.c om> wrote in message
news:c0******** *************** ***@posting.goo gle.com...

thanks for your quick reply to my email. i think what i try to say is
at the beginning, i want to give DB2 server 80% of memory (includes
you said global memory, db heap, .....), so it gives me
suggestion on the bufferpool size to 400000 pages, and some other
changes on locklist, package heap too, so i accept the changes, now
the bufferpool size is 400000 pages, but it gives me problem since i
have a application server hold on the same machine, i need to give it
memory too, so i decide i should let DB2 has only 40% of total memory,
give 40% memory to application server,
then i change only give DB2 to 40% of memory, but it gives me some
advice on logfilesize change, package cache size, but no advise on the
bufferpool size, so when i look at by control center, the size is
unchanged , i have to manually do it. shouldn't be advise change from
the advisor after i gives different memory request?

Does the DB2 command
AUTOCONFIGURE USING mem_percent 40 APPLY NONE
suggest different sizes?

Regards
Paul Vernon
Business Intelligence, IBM Global Services

[xixi]

one thing i noticed is that i used control center change the
bufferpool size IBMfefaultfb from 437471 to 250000, but the get db cfg
still gives me 437471, so which value DB2 is using? i am confusing