Memory Management in SAP ASE

Memory exists in SAP ASE as total logical or physical memory.

When SAP ASE starts, it allocates:

This figure illustrates how SAP ASE allocates memory as you change some of the memory configuration parameters:

Graphic of stratified images that describe how Adaptive Server’s memory is affected by adding additional logical memory. In the first image, the max memory is 15 MB, and the strata consist of the Adaptive Server binary, the kernel, user connections, procedure cache, the data caches, and the total logical memory is 10MB. In the second image, the max memory is still 15MB, but this image contains an additional strata of worker processes, so the total logical memory is now 12MB.

When a 2MB worker process pool is added to the SAP ASE memory configuration, the procedure and data caches maintain their originally configured sizes; 1.6MB and 5.3MB, respectively. Because max memory is 5MB larger than the total logical memory size, it easily absorbs the added memory pool. If the new worker process pool brings the size of the server above the limit of max memory, any command you issue to increase the worker process pool fails. If this happens, the total logical memory required for the new configuration is indicated in the sp_configure failure message. Set the value of max memory to a value greater than the total logical memory required by the new configuration. Then retry your sp_configure request.

Note: The values for max memory and total logical memory do not include the SAP ASE binary.

The size of the default data cache and the procedure cache has a significant impact on overall performance. See Performance and Tuning Series: Basics > Memory Use and Performance for recommendations on optimizing procedure cache size.