memory utilization advice

[Elena Leontieva]

Gentlemen,

DBA is going to reduce ora.init parameters, probably to pre-upgrade values.

I appreciate all your thoughts!
Elena.

[Tim Adamson_1]

Hi Elena,

I know I have come in on the end of this thread, but thought I would offer my 2 cents worth. If you dont want it, donate it to charity if you like :-)

As mentioned the buffer cache is WAY to small. By setting bufpages (or nbuf) to non-default values, you are not using dynamic bufer cache (ie, dbc_max_pct and dbc_min_pct are NOT used). The buffer cache is set to the bufpages value. I would recommend a buffer cache of at least 400Mb (and possibly higher). You would need to monitor things and increase it if necessary. I would also set bufpages back to the default (NBUF * 2) and use dynamic buffer cache but set dbc_max_pct to say 10 (this would mean a maximum buffer cache of 600Mb).

Secondly, I would add more swap. If you have lots of processes and they are reserving all your swap, then add more swap. The machine is there for people to use, not to be restricted.

The value of shmmax is quite large. Does it really need to be so big? It should be set to a value that is larger than the largest request the system should grant. By setting shmmax to a large value, you risk having a
process erroneously try to allocate a huge segment and consume all available swap space, only to be denied the request. Maybe this is what is happening in your case. Does the DBA really understand shmmax? Maybe he is confusing it with shared memory.

Anyway, just a few points. I'm sure I've added to the confusion and will keep a watch for the 2 cents when it is thrown back at me ;-)

[Carlos Fernandez Riera]

The amount of memory (reserved) show by swapinfo is only 4825, so in fact, it is enought memory. Maybe at any time, any process has used lots of memory.

I think you must change the point of view:

1-) Check the memory use: see how it grows and fall in a day basis. You will see any peaks, at online time or/and bacth time. How long are they?. At these times are you experienced performance issues?.

2-) There are some patches for memory leaks. One of them is mib2agt. It can consume lots of memory.

3-) I am surprised. Anybody has write about the use of :

UNIX95= ps -aef -o "pid,user,comm,sz,vsz" | sort -k 4n .

It is very useful to see the per process used memory. See man ps, or better, search UNIX95= in the forums.

Now you can see if your DBA is right or not.