CA-L-Serv › Define Managed Files › Buffer Pools › Determine the Size and Number of Buffers

Determine the Size and Number of Buffers

When you define LSR buffer pools, you must set the number of buffers per pool and the size of each buffer. Follow these guidelines to determine your number and size requirements:

Number of buffers

The number of buffers can affect system performance. If you define too few buffers of a given size, delays can occur in servicing I/O requests. If you define too many buffers, virtual storage is wasted.

Buffer size

The buffer size should correspond to the control interval (CI) size of the file. When VSAM reads a record, it needs a buffer that is at least as large as the CI size. Because VSAM files can have different buffer characteristics, buffer pools must be large enough to accommodate the CI size of the data and index portions of files without being wasteful.

Note: For more information about NSR and LSR pools as well as the IBM recommendations on determining an adequate size for your buffer pools, see the IBM publication DFSMS: Using Data Sets.