Memory usage always high and utiliaing full

[hariharan9985]

Dear All,

In our database, when checking the memory used using top command, we are always seeing 32 GB RAM utilized. We have set the sga_max_size to 8gb and PGA to 3 gb. We have tried shutting down oracle db and then the memory went down to 24GB when checked using top command. After cold reboot of the DB server, it gone down to 1.5 GB.

But once the users are started using after end of day, the memory again gone back to 32 GB.

Top Command output (truncated)
======================

top - 15:18:27 up 5 days, 19:43, 1 user, load average: 0.55, 0.39, 0.32
Tasks: 599 total, 3 running, 596 sleeping, 0 stopped, 0 zombie
Cpu(s): 1.5%us, 0.4%sy, 0.0%ni, 97.9%id, 0.1%wa, 0.0%hi, 0.1%si, 0.0%st
Mem: 32949628k total, 32823336k used, 126292k free, 238808k buffers
Swap: 8388600k total, 197308k used, 8191292k free, 25436196k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
16284 oracle 15 0 8352m 906m 890m S 11.6 2.8 2:59.27 oracle
28074 oracle 15 0 8333m 309m 300m S 11.6 1.0 1:28.33 oracle
13719 oracle 15 0 8346m 741m 726m R 4.6 2.3 0:30.55 oracle
19624 oracle 15 0 8338m 757m 745m R 0.7 2.4 0:52.04 oracle
32108 oracle 15 0 13000 1480 812 R 0.7 0.0 0:00.76 top
15542 oracle 15 0 8337m 627m 616m S 0.3 2.0 0:25.42 oracle
1 root 15 0 10344 676 564 S 0.0 0.0 0:05.49 init
2 root RT -5 0 0 0 S 0.0 0.0 0:00.06 migration/0
3 root 34 19 0 0 0 S 0.0 0.0 0:00.00 ksoftirqd/0
4 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/0
5 root RT -5 0 0 0 S 0.0 0.0 0:00.04 migration/1
6 root 34 19 0 0 0 S 0.0 0.0 0:00.00 ksoftirqd/1
7 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/1

OS : Red hat Enterprise Linux server release 5.3 (Tikanga)
DB : Oracle standard edition 10.2.0.1

Also please let me know, if the processes parameter(we have set 1000 and in v$resource_limit max is around 400) plays any role in this.

Regards,
Anand.

[coopstah13]

this question is asked so often, every time i see it it makes my head hurt

top does not show truly free/used memory, use free command to see this

linux memory management does not work the same as windows pre-vista/server 2008

[Rubberman]

this question is asked so often, every time i see it it makes my head hurt

top does not show truly free/used memory, use free command to see this

linux memory management does not work the same as windows pre-vista/server 2008

Indeed! Linux will use as much memory as it can for disc cache, which over time really speeds up the system. However, when it needs some of that memory for application code+data then it utilizes an LRU (Least Recently Used) algorithm to decide what parts of the cache it can best drop in order to release that memory to your applications. You should note that the amount of swap being used as shown by the 'top' command will, under normal circumstances, be 0 or some small value. For example, on my 8GB workstation it shows 280KB used, out of 16GB of swap space, yet it shows also that I have 2.5GB free core memory available. As coopstah said, the 'free' command is better for your purposes. In any case, don't be concerned unless 'top' shows that you have 0 or some very small value of core memory, and swap used is growing in size.