6. DATA SOURCES › 6.4 Query CP Parallelism Considerations › 6.4.2 Parallel Tasks Data Analysis › 6.4.2.1 Understanding Elapsed Time CA MICS Metrics

6.4.2.1 Understanding Elapsed Time CA MICS Metrics

In DB2, elapsed time is an important measurement because it
is used for several purposes.  From the end users
perspective, it is commonly considered as the response time
of a thread.  For the DB2 analyst, it is used in correlation
with other critical metrics, such as CPU time and I/Os for
performance analysis.  For query CP parallelism, it is
helpful to know the elapsed times of each individual parallel
task because it may help to determine how parallelism is
balanced (does every subtask have an "equal amount" of the
total work in terms of I/Os CPU, etc.).

The CA MICS files that provide a number of data elements
related to elapsed time measurements are the DB2 User
Activity (DB2DSU) and DB2 Plan Activity (DB2DSP) files.
Accurate reporting on threads elapsed time requires a good
understanding of the content of these variables, as soon as
parallel processing is involved.

The following table will help you with this task.  For
detailed information about each listed data element, see its
data dictionary entry.

+-----------------------------------------------------------+
!                                                           !
!          CONTENTS OF ELAPSED TIME DATA ELEMENTS           !
!                FOR THE DB2DSU/DB2DSP FILES                !
!                                                           !
+----------+----------------------+-------------------------+
!  Element !       Sequential     !       Parallel          !
!   Name   !       Processing     !      Processing         !
+----------+----------------------+-------------------------+
! fffELPTM ! thread total elapsed ! parent task elapsed     !
! fffET2TM ! time                 ! time only               !
+----------+----------------------+-------------------------+
! fffPELPT ! zero                 ! sum of all child tasks  !
! fffPET2T !                      ! elapsed times           !
+----------+----------------------+-------------------------+
! fffTELPT ! thread total elapsed ! sum of parent and all   !
! fffTET2T ! time                 ! child tasks elps. times !
+----------+----------------------+-------------------------+

For guidelines on how to use these data elements under
different perspectives, see Section 6.4.2.2 Data Analysis
Guidelines, later in this chapter.