What's the reasoning behind SAP's recommendation to use 20G of swap space with the 64bit kernel?
This has to do with the zero memory management recommendation. Many of the parameters in their zero memory management are cranked up very large. The theory is that in this way, the OS layer can handle the paging (since it is usually better than SAP). In general it is a good idea to go with a 1:3 memory to swap ratio but I have routinely operated under a 1:2 with no problems. If you are going to implement their "zero memory management" routine, you should have the 20 gigs of swap. OSS note 0153641 has many of the details.
This was first published in November 2001