IBM 5695-DF1 ユーザーズマニュアル

Case Study

145

Figure 63. DB2 PM Accounting, BP4 Section

12.1.3 Suspend Times

The class 3 section of the accounting report shows suspend (wait) times. This is
shown in Figure 64 on page 145. These values are only shown if the accounting
trace is started with class 3.

In this example, the wait times reported correspond to I/O. The application waited
56.77 seconds for synchronous reads (

) and 29 minutes and 59.16 seconds for

prefetch reads (

). This time is not directly attributable to the elapsed time,

because the I/O was performed in parallel. On Figure 57 on page 142 we have
the timing for parallelism. Only 3 minutes and 48.3 seconds (

in Figure 57) were

in the main task (TCB). The remainder, 27 minutes and 7.7 seconds (

in Figure

57) were performed in the five parallel tasks.

Figure 64. DB2 PM Accounting Class 3 Times

12.1.3.1 Synchronous I/O

Line

in Figure 64 on page 145 shows 19559 synchronous reads. This value is

also reported as the total synchronous reads made by this query,

in Figure 66

on page 147. The elapsed time for these reads is 56.770913 seconds. This gives
an average of 2.9 milliseconds for each read. This is a good response time for a
direct access to a page. This response time is also shown in the DB2 PM
highlights section,

in Figure 65 on page 146.

BP4

TOTAL

---------------------

--------

BPOOL HIT RATIO (%)

GETPAGES

300350 F

BUFFER UPDATES

SYNCHRONOUS WRITE

SYNCHRONOUS READ

754

SEQ. PREFETCH REQS

702

LIST PREFETCH REQS

DYN. PREFETCH REQS

3944

PAGES READ ASYNCHR.

148634

CLASS 3 SUSP.

ELAPSED TIME

EVENTS

--------------

------------

-------

LOCK/LATCH

0.060799

2760

SYNCHRON. I/O

56.770913

19559