increase the RAM size

[Former Member]

Hi all,

we are running ECC6 SR2 (kernel7.00) with Oracle 10.2.0.2 on our production servers. The Operating system was SuSE Linux 10 SP2 with 10 GB of RAM in Central instance and database instance ( central system).

Current RAM size : 10 GB

Current Swap space : 40 GB

Due to performance issues now we are planning to increase the memory to 32 GB on CI and DBI.

I want to know what are the steps that need to be done so that SAP will recognize that the available memory has increased.

thanks and regards

Ramesh

[hannes_kuehnemund]

Hi Ramesh,

this depends on your configuration of the SAP instance profile. If you have

es/implementation=std

(which should be the default sind 700 on 64-bit) simply set

es/initial_size_MB

to the new size. Make sure, that you substract the memory needed for DB + OS + reserve. As an example, in case you have 32GB memory, set it to 24576 (24GB) for SAP, 4GB for DB and leave 4GB for OS...

Thanks,

Hannes

[Former Member]

Hi,

I don't concure with Hannes - just 4GB for the DB is a bit small. I suggest you use 8 GB for the database and take 20GB for the SAP system. Ohterwise the DB will be a bottleneck and your instance can't make use of the additional RAM because the DB doesn't keep up.

Kind regards.

[hannes_kuehnemund]

Sven,

As an example, ...

I don't really think that Ramesh or anyone else would use example values ... they are too smart

Hannes

[Former Member]

Of course ;-D

It was just due to the proportions you stated - not that "someone" takes them too seriously (I've seen too many posts where the owner did not seem to at least have read the inst guides).

Kind regards.

[Former Member]

Hi,

thanks for your suggestions.,

1) i want to know what is the parameter to set the new value for Database.

i will set as follows (32 Gb memery)

SAP - 15 GB (em/initial_size_MB)

DB - 10 GB

Operating system - 7 GB

please correct me

2) currently we have allocated 40 GB for Swap space(10 GB RAM). whether it is required to increase the swap space ( according to new RAM value -32 GB )

regards

Ramesh

Edited by: Ramesh Sammiti on Oct 5, 2009 2:36 PM

[former_member524429]

Dear Ramesh,

The following SAP Notes may help you.

[Note 941735 - SAP memory management for 64-bit Linux systems|https://websmp130.sap-ag.de/sap%28bD1lbiZjPTAwMQ==%29/bc/bsp/spn/sapnotes/index2.htm?numm=146528]

[ Note 146289 - Parameter Recommendations for 64-Bit SAP Kernel|https://websmp230.sap-ag.de/sap%28bD1lbiZjPTAwMQ==%29/bc/bsp/spn/sapnotes/index2.htm?numm=146289]

Regards,

Bhavik G. Shroff

[Former Member]

Use the oracle parameter PGA_AGGREGATE_TARGET to specify the database's RAM allocation.

[Former Member]

Ramesh,

SAP - 15 GB (em/initial_size_MB)

Read [http://help.sap.com/saphelp_nw70/helpdata/EN/02/9626e7538111d1891b0000e8322f96/content.htm]

2) currently we have allocated 40 GB for Swap space(10 GB RAM). whether it is required to increase 
the swap space ( according to new RAM value -32 GB )

Ideally, you should have swap size 3 to 4 times of your RAM.'

Hope this helps.

Manoj

[hannes_kuehnemund]

Ideally, you should have swap size 3 to 4 times of your RAM

This is not necessarily a statement from SAP. SAP states in OS note [171356|https://service.sap.com/sap/support/notes/171356] that you should configure up to 2 times SWAP then physical memory is installed. This is valid up to 20GB of SWAP, more swap is only needed if you add additional SAP instances. for every additional SAP instance, SWAP should be increased by another 10GB. In case of more then 10GB of installed memory the recommendations are as follows:

1 Instance = 20GB SWAP

2 Instances = 30GB SWAP

3 Instances = 40GB SWAP

4 Instances = 50GB SWAP

...

Thanks,

Hannes

[Former Member]

Hannes,

On few occasions it is recommended more. Please check following note which suggests 3 times of RAM

Note 1112627 - SAP on HP-UX: Recommendations for swap and pseudo swap

Here onwards, I will refer to your note too as suggested earlier.

Thanks,

Manoj

[hannes_kuehnemund]

Manoj,

yeah, thats HP-UX and not Linux

The reason to have much more SWAP on UNIX then on Linux is, that memory on UNIX has to be backed 1:1 by SWAP and then you have to add additional SWAP on top of that value. Therefore for HP-UX it might be okay to have 3x SWAP then RAM.

But this forum is about Linux, and Linux is smarter then the old UNIX, so more SWAP does not give any additional benefit.

Thanks,

Hannes

[Former Member]

Hi,

After increased 32 GB RM in our servers, i checked in free command, it is showing that 160 MB free space. i am not understanding where the RAM is utilized

As per your suggestions, i had assigned 15 GB RAM to SAP (em/initial/size_MB ). But we did not get performance and also i want to know the database parameter for assigning the RAM.

And assigned SWAP - 40 GB and Available SWAP - 40 GB.

please give your suggestions and correct me

regards

Ramesh

[hannes_kuehnemund]

Ramesh,

if you give SAP 15GB and you have 32GB installed SWAP will not be used normally ... Also, please check SAP note 1382721 for explanation about the command 'free'.

You can get information, how much memory SAP is using per instance by calling transaction st02, then check the second box (maybe scroll down) which is named "SAP Memory". There you have to check "Extended Memory". This is exactly the memory SAP us using.

Thanks,

Hannes