Estimated duration of a job and related confidence factor

The estimated duration of a job run, and related confidence factor, are provided by logman as part of the daily planning cycle. The estimated duration of a job run is based on the average of its preceding runs, calculated analyzing five different time series: GLOBAL, WEEK_DAY, MONTH_DAY, MONTH_DAY_REVERSE, RUN_CYCLE. To compute the average run time for a job, logman divides the total run time for all successful runs by the number of successful runs. If a large number of runs is used to compute the average, a sudden change in a job's run time will not immediately be reflected in the average. To respond more quickly to such changes, you can use the smooth option so that the average can be weighted in favor of the most recent job runs. Use the -smooth option to enter a weighting factor, as a percentage, for current job runs. For example, the logman -smooth 40 command will cause logman to use a weighting factor of 40 percent for the most recent runs of the job, and 60 percent for the existing average. The logman -smooth 100 command will cause the most recent runs of the job to override the existing average. The default value for the -smooth option is 10.

Logman retains the statistical data of job runs in the HCL Workload Automation database. There is no limit to the number of job instances retained in the job history.

For each critical job, a percentage value indicates the confidence with which the critical job will meet its deadline. The confidence factor is calculated as the normal cumulative density function: it is the probability that the job will end within its deadline, calculated by using a Gaussian function, where the estimated end time is the mean and the estimated end variance is the standard deviation. To reduce the performance effort to a minimum, the confidence factor is calculated only when the estimated times are updated. Consequently, the value of the confidence factor always corresponds to the latest calculation.

A 95% confidence factor is associated to the estimated duration of a job. The confidence factor provides an estimated range of values, which is likely to include the job duration. For example, if the estimated duration of a job is 00:03:00, with a confidence factor of 00:00:05, it means that you can be 95% certain that the actual duration of the job is included between (00:03:00 - 00:00:05) and (00:03:00 + 00:00:05), that is, between 00:02:55 and 00:03:05.

When a new production plan is generated, you can display the estimated duration of a job, and the related confidence factor, by running the following command, from the conman command line:

showjobs job_name;props
You can display the same information from the Monitor Workload of the Dynamic Workload Console.
Under certain conditions, you might decide to override the estimated duration of a job, for example:
  • For a new job, whose estimated duration is set, by default, to 00:00:00. You might want to set the estimated duration to an initial value that is more realistic, based on your experience.
  • For a job whose estimated duration has a high confidence factor. You might want to change the job scheduling and, consequently, its estimated duration.
Once the job completes, the confidence factor is set to 0% when the estimated duration is exceeded and when the estimated duration is not exceeded, the confidence factor is set to 100%. While statistical data is collected, the estimated duration that you set is replaced by logman, according to the algorithm described above.

You can override the estimated duration of a job in a job stream from the Workload Designer of the Dynamic Workload Console.

An alternative tool that provides estimated job duration forecasts and confidence intervals through the same media is based on machine learning algorithms. See Predicting job duration using AI-based algorithms for details.