Analyzing memory usage by db2agents

[Ember]

For once, I have a customer that is more concerned with reducing the
memory usage than with increasing performance - a new direction in
tuning for me. I'm looking at db2 agent processes on the system - db2
7.2 fp 11 on RH Linux - no parallelism (neither inter or intra
partition). There are generally about 14 connections and therefore
about 14 db2agents. OS analysis shows that each agent is using in the
range of 260 - 270 MB of memory. Looking at the configuration and the
parameters which affect the maximum amount of memory used by a
db2agent, I come up with about 20 MB as the upper limit:
applheapsz = 2048
sortheap = 256
stmtheap = 2048
aslheapsz = 1000
DRDA heap, UDF shared memory, and statistics heap size are irrelevant
because none of them are used on this system. (no, we don't do
runstats, but I'm trying to talk them into it ... another story)

What am I missing in my calculations here? why are the agents using
this much memory?

Thanks,

Ember Crooks

[Ian]

Ember wrote:

For once, I have a customer that is more concerned with reducing the
memory usage than with increasing performance - a new direction in
tuning for me. I'm looking at db2 agent processes on the system - db2
7.2 fp 11 on RH Linux - no parallelism (neither inter or intra
partition). There are generally about 14 connections and therefore
about 14 db2agents. OS analysis shows that each agent is using in the
range of 260 - 270 MB of memory. Looking at the configuration and the
parameters which affect the maximum amount of memory used by a
db2agent, I come up with about 20 MB as the upper limit:
applheapsz = 2048
sortheap = 256
stmtheap = 2048
aslheapsz = 1000
DRDA heap, UDF shared memory, and statistics heap size are irrelevant
because none of them are used on this system. (no, we don't do
runstats, but I'm trying to talk them into it ... another story)

What am I missing in my calculations here? why are the agents using
this much memory?

You didn't say how you're calculating the number (260-270 Mb), but
generally the numbers you get from 'ps' show the total memory associated
with the process, including shared memory segments that the agents have
attached to (i.e. bufferpools).


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[Fan Ruo Xin]

"Ian" <ia*****@mobileaudio.com> wrote in message
news:40********@corp.newsgroups.com...

Ember wrote:

For once, I have a customer that is more concerned with reducing the
memory usage than with increasing performance - a new direction in
tuning for me. I'm looking at db2 agent processes on the system - db2
7.2 fp 11 on RH Linux - no parallelism (neither inter or intra
partition). There are generally about 14 connections and therefore
about 14 db2agents. OS analysis shows that each agent is using in the
range of 260 - 270 MB of memory. Looking at the configuration and the
parameters which affect the maximum amount of memory used by a
db2agent, I come up with about 20 MB as the upper limit:
applheapsz = 2048
sortheap = 256
stmtheap = 2048
aslheapsz = 1000
DRDA heap, UDF shared memory, and statistics heap size are irrelevant
because none of them are used on this system. (no, we don't do
runstats, but I'm trying to talk them into it ... another story)

What am I missing in my calculations here? why are the agents using
this much memory?
You didn't say how you're calculating the number (260-270 Mb), but
generally the numbers you get from 'ps' show the total memory associated
with the process, including shared memory segments that the agents have
attached to (i.e. bufferpools).

I agree with Ian. You must add part of the shared memory into your total
number. The snapshot output from version8.1 will give us more ideas about
the db2 memory/heap usage than version7.

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