How SAP ASE Allocates Buffer Pools

SAP ASE allocates buffer pools in units of logical pages.

For example, on a server using 2K logical pages, 8MB are allocated to the default data cache. This constitutes approximately 2048 buffers. If you allocated the same 8MB for the default data cache on a server using a 16K logical page size, the default data cache is approximately 256 buffers. On a busy system, this small number of buffers might result in a buffer always being in the wash region, causing a slowdown for tasks that request clean buffers. In general, to obtain the same buffer management characteristics on larger page sizes as with 2K logical page sizes, scale the size of the caches to the larger page size. So, if you increase your logical page size by four times, your cache and pool sizes should be about four times larger as well.

SAP ASE typically allocates memory dynamically and allocates memory for row processing as it needs it, allocating the maximum size for these buffers, even if large buffers are unnecessary. These memory management requests may cause SAP ASE to have a marginal loss in performance when handling wide-character data.