Most of the constraints allow you to specify a maximum value and a corresponding minimum value. For example, you can specify both a maximum and a minimum allowable buffer space. CA Hyper-Buf implements a value that falls between the specified high and low values, as long as it does not conflict with other constraints.
If you specify MINBUFND=10, MAXBUFND=50, and MAXBUFSP=60K, CA Hyper-Buf uses between 10 and 50 data buffers, as long as the resultant buffer space does not exceed 60K.
Note: The index component also uses part of this buffer space, so you may not actually have 60K of data buffers).
Any user specified MINxxx constraints are validated by the CA Hyper-Buf OPEN intercept routine. The user specified MINxxx constraints are compared with the minimum VSAM allowable values. If the user specified values are less than the VSAM allowed minimum values, the user values are increased to the VSAM minimum.
For example, if an ACB specifies STRNO=4 and is associated with a cluster that has a 4K data CI size and a 2K index CI size, the true minimum allowable VSAM buffer space (NSR) for this file is 28K. If the user has specified MINBUFSP=12K, the CA Hyper-Buf OPEN intercept routine overrides the user value, and use 22K as the MINBUFSP value.
If any minimum constraint value exceeds the corresponding maximum constraint value (after the constraint merge is complete), the maximum constraint is increased to the value of the minimum constraint. For example, if after all constraint merging is complete, MAXBUFSP=40K and MINBUFSP=60K, then MAXBUFSP is increased to 60K, which is the MINBUFSP value.
In most cases, you do not need to specify any minimum values. CA Hyper-Buf calculates an optimum number of buffers, without exceeding any maximum value that you have specified. For example, assume that the composite constraints are MAXBUFSP=52K, MAXBUFND=8, data CI size is 10K, and no index buffers are required (for example, an ESDS file). CA Hyper-Buf can assign five data buffers for a total of 50K buffer space (depending upon devicetype, OPEN options, and so forth), which is as close to MAXBUFSP as possible with this particular file. Specifying a minimum value has no effect in this case.
Consider setting minimums if you specify SEQUENTIAL, RANDOM, or CICS constraints for any level. For example, if you specify the SEQUENTIAL processing constraint for a KSDS because access is predominantly sequential, CA Hyper-Buf acquires only one index buffer per string and as many data buffers as reasonable. This processing is optimized for sequential processing. If the application also has some amount of random processing, you may be able to improve performance by increasing the number of index buffers. You can ensure that more index buffers are allocated by specifying a larger MINBUFNI.
Each constraint is associated with the LEVEL SELECTOR that precedes it in the control stream.
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