The explanation can be found in the driver program used to run the query. This program does a CONNECT RESET automatically after each query.

SQL DCL

TOTAL

 

----------

--------

 

LOCK TABLE

0

 

GRANT

0

 

REVOKE

0

 

SET SQLID

0

 

SET H.VAR.

0

 

SET DEGREE

1

L

SET RULES

0

 

CONNECT 1

0

 

CONNECT 2

1

M

SET CONNEC

0

 

RELEASE

0

 

CALL

0

 

ASSOC LOC.

0

 

ALLOC CUR.

0

 

DCL-ALL

2

 

Figure 59. DB2 PM Accounting, SQL DCL Section

QUERY PARALLEL.

TOTAL

 

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

--------

 

MAXIMUM MEMBERS

N/P

 

MAXIMUM DEGREE

5

N

GROUPS EXECUTED

1

O

RAN AS PLANNED

1

P

RAN REDUCED

0

 

ONE DB2 COOR=N

0

 

ONE DB2 ISOLAT

0

 

SEQ - CURSOR

0

 

SEQ - NO ESA

0

 

SEQ - NO BUF

0

 

SEQ - ENCL.SER

0

 

MEMB SKIPPED(%)

0

 

DISABLED BY RLF

NO

 

Figure 60. DB2 PM Accounting, Parallel Query Section

12.1.1.3 Time Not Accounted

H in Figure 57 on page 142 shows 19 minutes 50 seconds of time not accounted for. This is the time the main TCB had to wait for all the parallel threads to finish.

Without query parallelism, the time not accounted for is defined as the difference between class 2 and class 3 times (class 2 - class 3). This formula works when there is only one TCB.

With query parallelism, this formula no longer works. Class 2 time is associated with the main TCB only, since it represents the DB2 time of a query. However, class 3 time is associated with each parallel task (SRB) plus the main TCB, and the sum of all the class 3 times can be much longer than the class 2 time. As a result, DB2 PM decides to report on the main TCB only. Again, the time not accounted for is still class 2 - class 3, but associated with the main TCB only. Since the main TCB can wait for a long time for all the parallel tasks to complete, as is the case where a query scans a large tablespace, the time not accounted for can be quite long.

Case Study 143

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IBM 5695-DF1, 5655-DB2 manual Time Not Accounted

5695-DF1, 5655-DB2 specifications

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