DB2 Understanding Elapsed Time MICS Metrics
MICS
MetricsIn DB2, elapsed time is an important measurement because it is used for several purposes. From the end-user perspective, it is commonly considered as the response time of a thread.
micsrm140cd
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 might help to determine how parallelism is balanced. For example, does every subtask have an "equal amount" of the total work in terms of I/Os CPU, and so on.
The
MICS
files that provide several data elements that are 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.Contents of Elapsed Time Data Elements for the DB2DSU/DB2DSP Files
Element Name | Sequential Processing | Parallel Processing |
fffELPTM | thread total elapsed time | parent task elapsed time only |
fffET2TM | thread total elapsed time | parent task elapsed time only |
fffPELPT | zero | sum of all child tasks elapsed times |
fffPET2T | zero | sum of all child tasks elapsed times |
fffTELPT | thread total elapsed time | sum of parent and all child tasks elapsed times |
fffTET2T | thread total elapsed time | sum of parent and all child tasks elapsed times |
For guidelines on how to use these data elements under different perspectives, see DB2 Data Analysis Guidelines.