It is difficult, if not impossible, to select a buffer space at DEFINE time that optimizes the performance of the wide range of applications and access patterns that are found in a production environment. Most files have several applications accessing them, including sequential backups and reorgs, audits, random online inquiries, and batch reports. Each of these applications has a different accessing pattern, which requires buffering adjustments to perform optimally. While specifying a larger buffer space in the catalog usually improves performance, it does not result in the best possible performance for each application that accesses a file. Some applications are better served by the catalogued buffer space than others. Also, the specified buffer space can waste virtual storage, possibly causing VSAM to allocate more index buffers than are required to buffer the entire index set. These excess buffers are not useful, and the virtual storage thus tied up could be put to better use elsewhere.
|
Copyright © 2011 CA.
All rights reserved.
|
|