Question Re: em/initial_size_MB / Physical RAM in Technology Q&A

em/initial_size_MB / Physical RAM

Former Member — Tue, 14 Oct 2014 14:49:40 GMT

Hello,

I have a client who is experiencing some performance issues so I'm just reviewing the memory parameters/allocations.

Environment is Windows/SQL.

The box has 8GB of physical memory with 24GB of virtual memory.

em/initial_size_MB is set to 10GB.

I have in the back of my mind that em/initial_size_MB should not be greater than the amount of physical memory. Is that correct? And if it's set to a higher value, what issues could it cause?

Many thanks.

Re: em/initial_size_MB / Physical RAM

Former Member — Tue, 14 Oct 2014 15:02:45 GMT

Hi Paul ,

Check the below sap note

88416 - Zero administration memory management for the ABAP server

The parameter above has some limitation for kernel as well.

For the same checked the sapnote

1458065 - Extended memory restricted to 64G

835474 - More than 32 GB extended memory

With Regards

Ashutosh Chaturvedi

Re: em/initial_size_MB / Physical RAM

Former Member — Tue, 14 Oct 2014 15:14:54 GMT

Thanks for the suggestions.

So note 88416 suggests that em/initial_size_MB should be equal to PHYS_MEMSIZE??

PHYS_MEMSIZE does not exist in this particular system.

Presumably it will just be the value of the of the amount of RAM in the box?

In which, I need to be reducing em/initial_size_MB to 8GB?

Re: em/initial_size_MB / Physical RAM

Former Member — Tue, 14 Oct 2014 15:24:32 GMT

Hi Paul,

Whats your kernel version?

With Regards

Ashutosh

Re: em/initial_size_MB / Physical RAM

Former Member — Tue, 14 Oct 2014 15:29:35 GMT

721 EXT Unicode - Patch Level 201

Re: em/initial_size_MB / Physical RAM

Former Member — Tue, 14 Oct 2014 15:34:42 GMT

Hi Paul,

Then Zero administartion sapnote fits the kernel requirement.

You can wait for others to reply on your thread to have a good picture of the parameters.

With Regards

Ashutosh Chaturvedi

Re: em/initial_size_MB / Physical RAM

Reagan — Tue, 14 Oct 2014 20:24:29 GMT

The SAP note 88416 - Zero administration memory management for the ABAP server suggested by Ashutosh is the answer. If the parameter PHYS_MEMSIZE is not set then you should set it.

1926986 - Best practice formulas in profile maintenance

Re: em/initial_size_MB / Physical RAM

Former Member — Wed, 15 Oct 2014 09:16:45 GMT

Hi Paul,

em/initial_size_MB value should never be more the physical memory available to the SAP instance.

PHYS_MEMSIZE:

If you have only SAP instance running on the host than you don't need to set the value for it.

Else set it accordingly to available space

Formula:

PHYS_MEMSIZE = Available main memory for the SAP instance

The default value for PHYS_MEMSIZE is the size of the main memory in MB, that is, it is adjusted automatically when the main memory configuration is changed.

em/initial_size_MB = [PHYS_MEMSIZE]

If required, the extended memory extends itself by the value [PHYS_MEMSIZE / 2].

Example: Application server with 1 GB main memory.

PHYS_MEMSIZE is not maintained and its default value is the size of the main memory. This means that the initial size of the extended memory = 1 GB. If this size is not sufficient, the extended memory is increased in 500 MB steps until the maximum size em/max_size_MB (default: 20 GB) is reached or until there is no more address space in the NT page file.

Hope this helps you out.

Regards,

Prithviraj

Re: em/initial_size_MB / Physical RAM

Former Member — Wed, 15 Oct 2014 09:31:58 GMT

Hi,

These are all extremely helpful replies, thank you.

I can pad this out now with a little bit more information. PHYS_MEMSIZE is set, I was searching RZ11 for PHYS* - this doesn't work. Putting in the PHYS_MEMSIZE does!

This is set to 10GB. I don't see how as this is automatically set from the amount of RAM in the box right? And that is 8GB!

Also, ST04 shows 3GB is fixed. So only 5GB left to play with. But PHYS_MEMSIZE and em/initial_size_MB is set to 10GB.

All a bit messy really.

Re: em/initial_size_MB / Physical RAM

S_Sriram — Wed, 15 Oct 2014 09:47:41 GMT

Hi Paul

As per the SAP stranded you have to set the memory 70% Application & 30% Database.

1. In your MS SQL server memory resource should not cross more than 30 % of memory? If it is yes, you can set the memory parameters in MS SQL MMC

2. Balance amount 70% of memory can be used for application & OS

3. You can restart the system check the transaction code ST02 memory & buffer usage Is this any swaps?

4. Check the DB over all usage? refer the SCN link how you can fine trun the DB?

Regards

Sriram