Creating a Compression Memory Pool

When SAP ASE reads a page from a compressed dump, it selects a compressed block from the dump, decompresses it, and extracts the required page.

The decompression in SAP ASE is done using large buffers from a special memory pool.

Configure the size of the pool using:
sp_configure ‘compression memory size’, size

This is a dynamic configuration parameter, and the size is given in 2KB pages. If size is set to 0, no pool is created, and you cannot load a compressed dump.

To determine the optimal size for your pool, consider these two factors:

  • The block I/O used by the Backup Server. By default, this block I/O is 64KB, but it could have been changed using the with blocksize option in the dump database command.

  • The number of concurrent users decompressing blocks within all archive databases. Each concurrent user requires two buffers, each the same size as the block I/O.

As an absolute minimum, allow one concurrent user two buffers per archive database.