Swap Space Size: Oracle 11g on RHEL 6

[Former Member]

Hello;

I found SAP Note 1597355 which discusses the possible size of a LINUX OS swap file when SAP is installed. When I reviewed this file, it appears to be dated from July of 2011. My question(s) are these:

1.) Is there any newer guidance on this topic for cases when Oracle 11g may be used.

2.) According to Oracle, a swap file-size of 16GB is sufficient if the allocated RAM is 16GB or more.

My situation is I'll have RHEL 6 VM's of 64, 96, & 128 GB RAM. If I went by what's in SAP Note 1597355 I'd need to reserve an OS Swap resource of ~100GB for each VM. If I followed Oracle, I'd only allocate 16GB of Swap per VM (a savings of 84GB per VM which is not trivial over 10's or hundreds of VM's). Any advice on this topic would be great.

Thanks In Advance

[former_member188883 · Accepted solution]

Hi David,

As I see that you have enough RAM configured for each VM. Technically Swap space will be utilized only when RAM is not sufficient. So initially you may configure a lower value say 20GB which is good to start on Unix environments.

Later based on system utilization you may evaluate and increase swap space if required.

Hope this helps.

Regards,

Deepak Kori

[Former Member · Accepted solution]

Many thanks to the folks who answered my question!

I certainly appreciate it.

[Former Member · Accepted solution]

Well...

Sadly, when I took the advice I was given above and presented it to my internal colleagues, they shot-me-down. They decided instead to follow a policy of strict adherence to SAP Note 1597355. This means swapfile allocations of 96GB or more for VM's that use 64GB of RAM or greater. Shame SAP has not come out with a newer SAP note on this topic. Guess its time to buy more EMC or HP stock (Since we have to use EMC or HP 3Par disk).

[Former Member · Accepted solution]

Hi David,

i believe you are following a rule of 1.5x. Some other MS bulletin will indicate 2x of your physical RAM.

EVen the note you have mentioned is not the most updated. I just setup some system and remember reading either from the master or install guide to follow a formula.

It is based on the number of WPs or java processes x some figures; whether DB is integrated and something like that.

THat calculation will be more accurate.

[nicholas_chang]

Hi David,

if i not mistaken, if you go thru the installation guide, the min of 20GB swap space should be safe. In our environment, we would just set 20GB swap space as standard practice, and never encounter any swap issue.

Also, as per note 1597355:

"Customers may decide to use more or less swap-space based on their individual system configuration and their own experience during the day-to-day usage of a system."

my 2 cents worth.

Cheers,

Nicholas Chang