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I/O Performance and Monitoring Tools 121
Figure 44. DB2 PM Accounting, Buffer Pool Section
11.1.1.2 I/O Suspensions
If accounting trace class 3 is activated, the DB2 accounting reports show a
summary of the wait times of a DB2 application. This summary shows when the
DB2 application is suspended (waiting) for a DB2 system task to complete. These
suspensions include the waits for I/O operations.
Figure 64 on page 145 shows an example of class 3 suspend times. The values
shown for
A, B, C are total elapsed times for I/O and the number of occurrences
of each type of I/O (events).
A: SYNCHRON. I/O The total elapsed time due to synchronous I/O
and the total number of synchronous I/O
suspensions.
B: OTHER READ I/O The total waiting time due to asynchronous
read I/O and the total number of suspensions
due to asynchronous read I/O.
C: OTHER WRTE I/O The total elapsed time due to asynchronous
write I/O and the total number of
asynchronous write I/O suspensions.
Note: Another example of other write I/O is the case in which a transaction is
waiting because the page that the transaction wants to update is currently being
written out by a write engine. In this case, the wait time is captured in other write
I/O.
Note: Wait time for force at commit time is included in SYNC I/O WAIT with V5
and LOG FORCE WRITE WAIT with V6.
11.1.2 Statistics I/O Information
11.1.2.1 Data I/O Operations
The statistics report provides detailed information on I/O operations for each
buffer pool at the DB2 susbsystem level. This means that this report summarizes
the information of all applications executing during the interval that statistics are
gathered. The information provided is much more detailed than the information in
BP4 TOTAL
--------------------- --------
BPOOL HIT RATIO (%) 50
GETPAGES 300350
BUFFER UPDATES 0
SYNCHRONOUS WRITE 0
SYNCHRONOUS READ 754
SEQ. PREFETCH REQS 702
LIST PREFETCH REQS 0
DYN. PREFETCH REQS 3944
PAGES READ ASYNCHR. 148634
HPOOL WRITES 0
HPOOL WRITES-FAILED 0
PAGES READ ASYN-HPOOL 0
HPOOL READS 0
HPOOL READS-FAILED 0