You can use the SHOWCB macro to obtain statistics about the use of buffer pools. These statistics help you determine how to improve both a previous definition of a resource pool and the mix of data sets that use it. The statistics are available through an ACB that describes an open data set that is using the buffer pool. They reflect the use of the buffer pool from the time it was built to the time SHOWCB is issued. All but one of the statistics are for a single buffer pool. To get statistics for the whole resource pool, issue SHOWCB for each of its buffer pools.

The statistics cannot be used to redefine the resource pool while it is in use. You have to make adjustments the next time you build it.

The use of SHOWCB to display an ACB is described in Manipulating the Contents of Control Blocks. If the ACB has MACRF=GSR, the program that issues SHOWCB must be in supervisor state with protection key 0 - 7. A program check can occur if SHOWCB is issued by a program that is not in supervisor state with the same protection key as the resource pool.

For buffer pool statistics, the keywords described below are specified in FIELDS. These fields may be displayed only after the data set described by the ACB is opened. Each field requires one fullword in the display work area:

Field	Description
BFRFND	The number of requests for retrieval that could be satisfied without an I/O operation (the data was found in a buffer).
BUFNOL	The number of I/O buffers allocated for the data component or index component during BLDVRP or SMB for LSR processing.
BUFRDS	The number of reads to bring data into a buffer.
BUFUSE	The number of I/O buffers actually in use for the data component or index component at the time the SHOWCB macro issued.
NUIW	The number of nonuser-initiated writes (that VSAM was forced to do because no buffers were available for reading the contents of a control interval).
STRMAX	The maximum number of placeholders currently active for the resource pool (for all the buffer pools in it).
UIW	The number of user-initiated writes (PUTs not deferred or WRTBFRs, see Deferring Write Requests).