# Buffer pool summary report

The buffer pool section of the summary report contains selected fields from the full buffer pool report.

- TOTAL I/O REQUESTS
- The total number of I/O requests (TOTALS) and the average elapsed time per I/O request (AET).
*Calculation of TOTALS*: count of matching IFCID 006 and 007 record pairs (read requests) + matching IFCID 008 and 009 record pairs (synchronous writes) + matching IFCID 009 and 010 record pairs (asynchronous writes)*Calculation of AET*: (sum of differences in the store clock values DB2® field QWHSSTCK of matching IFCID 006 and 007 + IFCID 008 and 009 + IFCID 009 and 010 record pairs) / (count of matching IFCID 006 and 007 + IFCID 008 and 009 + IFCID 009 and 010 record pairs) - TOTAL READ I/O REQUESTS
- The total number of I/O read requests (TOTALS) and the average elapsed time per read request
(AET).
- NON-PREFETCH READS
- The total number of non-prefetch reads.
*Calculation*: count of IFCID 006 and 007 record pairs, with DB2 field QW0006F equal to RNote: For consistency with the existing non-prefetch reads field, the average time is not calculated for the zHyperLink I/Os or the I/Os with disk cache hits.- ZHYPERLINK
- The total number of non-prefetch reads that used zHyperLink.
- DISK CACHE HIT
- The total number of non-prefetch reads where all the requested pages were found in the DASD subsystem cache.

- PREFETCH READS
- An aggregate of all types of prefetches:
- Sequential prefetches (determined at bind time)
- List prefetch
- Sequential prefetch triggered by the sequential detection logic

- WITHOUT I/O
- The number of unsuccessful prefetch reads. This can occur because all the pages requested by a
prefetch read were already in the buffer pool.
*Calculation*: count of matching IFCID 006 and 007 record pairs, with DB2 field QW0006F not equal to R (type of read request) and DB2 field QW0007NP equal to zero (indicating no pages were read) - WITH I/O
- The number of successful prefetch reads.
*Calculation*: count of matching IFCID 006 and 007 record pairs, with DB2 field QW0006F not equal to R (type of request) and DB2 field QW0007NP greater than zero (number of pages read) - PAGES READ
- The number of pages read for all prefetch read requests.
*Calculation*: sum of DB2 field QW0007NP with DB2 field QW0006F not equal to R - PAGES READ / SUCC READ
- The number of pages read per successful prefetch read request.
*Calculation*: (sum of DB2 field QW0007NP with DB2 field QW0006F not equal to R) / (count of matching IFCID 006 and 007 record pairs, with QW0006F not equal to R and QW0007NP greater than zero)

*Calculation of TOTALS*: count of matching IFCID 006 and 007 record pairs*Calculation of AET*: (sum of differences in the store clock values DB2 field QWHSSTCK of matching IFCID 006 and 007 record pairs) / (count of matching IFCID 006 and 007 record pairs) - TOTAL WRITE REQUESTS
- The total number of write I/O requests (TOTALS) and the average elapsed time per write request
(AET).
*Calculation of TOTALS*: count of matching IFCID 008 and 009 (synchronous writes) + IFCID 009 and 010 record pairs (asynchronous writes)*Calculation of AET*: (sum of differences in the store clock values DB2 field QWHSSTCK of matching IFCID 008 and 009 record pairs (for synchronous writes) + matching IFCID 010 and 009 record pairs (for asynchronous writes)) / (count of matching IFCID 008 and 009 record pairs + matching IFCID 009 and 010 record pairs)The write requests are divided into two categories: synchronous writes and asynchronous writes.- SYNCHRONOUS WRITES
- The number of synchronous writes (TOTALS) and the average elapsed time per synchronous write
request (AET).
- COUPLING FACILITY CASTOUTS
- The number of synchronous writes due to coupling facility castouts.
*Calculation*: QW0008FC / QW0010FC - PAGES WRITTEN PER WRITE
- The average number of pages per synchronous write.
*Calculation*: (sum of DB2 field QW0008WR) / (count of matching IFCID 008 and 009 record pairs)

*Calculation of TOTALS*: count of matching IFCID 008 and 009 record pairs*Calculation of AET*: (sum of differences in the store clock values DB2 field QWHSSTCK of matching IFCID 008 and 009 record pairs) / (count of matching IFCID 008 and 009 record pairs) - ASYNCHRONOUS WRITES
- The number of asynchronous writes (TOTALS) and the average elapsed time per asynchronous write
(AET).
- COUPLING FACILITY CASTOUTS
- The number of asynchronous writes due to coupling facility castouts.
*Calculation*: QW0008FC / QW0010FC - PAGES WRITTEN PER WRITE
- The average number of pages written per asynchronous write.
*Calculation*: (sum of DB2 field QW0010WR) / (count of matching IFCID 009 and 010 record pairs)

*Calculation of TOTALS*: count of matching IFCID 009 and 010 record pairs*Calculation of AET*: (sum of differences in the store clock values DB2 field QWHSSTCK of matching 9 and 10 record pairs) / (count of matching IFCID 009 and 010 record pairs)