Legends don't die or fade away. Not even the ones about SAP and pagefiles

By Renegade on Friday 7 August 2009 13:43 - Comments (6)
Categories: General, SAP, Views: 3.945

Some things just stay around. You can try to tell people that it's just not true, but they won't believe you, or they will just ignore of forget the things you tell them.

One of the most heard things about SAP and hardware resources is that you need at least twice the amount of RAM configured as swap or as a paging file. Sometimes you will even hear that you need up to three of four times the RAM.

Now, this was actually true.... In 2003 or so. 8)7

Nonetheless I still receive mails about this recommendation. One that came in today was something along these lines:
The SAP installation guide recommendations that the amount of swap space on the server be twice the amount of RAM - this recommendation is valid for Database, Central Instance, and DIA instances.

The following servers all have 32GB of RAM allocated to them. They also all have 32GB of swap configured. In order to comply with the prerequisites we'll need to increase the swap space on each to 64GB as soon as possible.
Now, this would still be ok if we were talking about physical machines that are relatively small. If there wasn't the fact that we also have servers that are quite a bit bigger and carry 256GB of RAM on them. Configuring 2x the amount RAM or even 4x that amount would just be a waste of disk space, and to get this part written down:

I'ts no longer required on IA64 and x64!

People wrote down the numbers of some SAP notes once, and they continue to refer to these same notes instead of just checking if there perhaps is an updated version of it flying around somewhere.

Now this could spark up an entirely different discussion about versioning of documents and the ability to locally store copies of documents. Anyone would have a blast at an ISO 20000 audit. :+

Anyway, to get rid of the rumors in this post, at this point in time you can check the following SAP note #146289 (link may require a valid service marketplace account) which in a nutshell states the following:
When implementing the 64-bit kernel, we recommend at least
20 GByte of swap space. (Plus approx.10 GB for every additional 64-bit instance on the same computer) See note 153641 for more information.
And this is valid for all installations with a 64-bit kernel. If you want to print it, add a date of the last change, or just subscribe to the document, and remember to perhaps check after a year or so if some newer info is available. After all we are working in the IT-business and things do tend to change every now and then. ;)