The BUFFERSPACE parameter specifies the number of bytes of virtual storage reserved for buffers when the file is opened. VSAM open processing GETMAINs BUFFERSPACE bytes of storage. VSAM then subdivides this block of storage into individual data buffers and, if the file is a KSDS, index buffers. The following diagram shows BUFFERSPACE bytes of storage subdivided into six index and three data buffers.
For KSDS files using NSR buffering, VSAM subdivides the BUFFERSPACE area into some number of buffers for data control intervals, and some number for index control intervals. The actual number of each type depends upon the number of bytes available for buffers (BUFFERSPACE), the ACB MACRF options specified at OPEN time (DIR, SEQ, or both), and the CI sizes of the data and index components.
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