topic Oracle + Linux Memory doubt in Operating System - Linux

Oracle + Linux Memory doubt

Leonardio — Thu, 22 Oct 2009 13:12:33 GMT

Hi friends

I have a server with 11GB RAM and 12GB swap space.
And started 11 databases with sum of SGA =~ 7.5GB
When I try start a other database, with a SGA=400MB, the Oracle returns
-----
SQL> startup nomount
ORA-27102: out of memory
Linux Error: 28: No space left on device
-----

Why out of memory, if only 7.5GB was used?

I attached the commands ipcs e free -m. I know that the free command doesn't show a real state of free memory, because Linux, use cache/uncache frequently, but the ipcs command show only 7.5GB used.. and donÂ´t have many users connections in this server.

Tks
Leonardo Mantovam

Re: Oracle + Linux Memory doubt

Leonardio — Thu, 22 Oct 2009 13:21:26 GMT

Attch

Re: Oracle + Linux Memory doubt

Court Campbell — Thu, 22 Oct 2009 13:22:34 GMT

More info is needed. What Linux distro is this? Also are you running 64-bit or 32-bit with the hugemem kernel? Can you post the output from the free command? Also, what are your shmem kernel settings?

Re: Oracle + Linux Memory doubt

Court Campbell — Thu, 22 Oct 2009 14:24:42 GMT

change shmall to 2883584. shmall sets the total amount of shared memory pages that can be allocated system wide. So if you take shmall x page size you can get the amount. In your case your page size is more than likely 4096. So that would limit you to 8GB for shared memory pages. Increase it and you should be good to go.

Re: Oracle + Linux Memory doubt

Leonardio — Thu, 22 Oct 2009 16:16:59 GMT

Court,

Thanks for your reply
The Oracle Documents doesn't show this tips.

But more a question if I want use the swap space too, so I need change the value that you already posted, 2883584(shmmall) X 4096(page size) = 11GB.

In other hands, increase the 2883584 to 2883584 x 2 ( 22GB ) the sum of mem+swap??

I know that the Oracle will be slower
, but this databases are only to enviroment development

Tks
Leonardo Mantovam

Re: Oracle + Linux Memory doubt

Steven E. Protter — Thu, 22 Oct 2009 18:10:48 GMT

Shalom,

With regards to swap space, if you set it to more than twice ram that in itself is not a problem.

if however the system starts paging, performance will grind to a halt.

If you have to set swap more than twice ram to make oracle run, this is not the system to run oracle on.

SEP

Re: Oracle + Linux Memory doubt

Leonardio — Fri, 23 Oct 2009 12:59:32 GMT

Steve,

I know that Oracle doesn't have a good performance if begins to use swap space, but this machine are only development enviroment so performace, isn't important.

Now I changed the value of shmmall to 2883584, and started more database, without used swap space. 2883584 x 4096=11GB (memory of machine)
----
free -mt
total used free shared buffers cached
Mem: 11159 10247 912 0 130 9195
-/+ buffers/cache: 920 10238
Swap: 12699 267 12432
Total: 23859 10514 13345
----
This machine has 11GB the swap.
My doubt. If I increase shmmall(2883584), I started to use the swap ?

I want start more databases.

Tks
Leonardo Mantovam