Interpreting Report Class Data

Through classification rules WLM allows you to associate transactions with report classes for reporting purposes only. Report classes can be used to report on a subset of transactions running in a single service class but also combine transactions running in different service classes within one report class. In the first case a report class is called homogeneous, and in the second case it is called heterogeneous.

Before z/OS® V1R2, WLM only returned a report class summary.

Since z/OS V1R2 WLM returns report class periods. A report class period is homogeneous if there is only one service class found contributing to this report class period in a given report interval. To allow a reporting product to determine whether a report class period is homogeneous in its reporting interval, WLM offers two indicators returned by IWMRCOLL:

mixed-class-indication timestamp

This timestamp indicates when workload data associated with a different service class last contributed data to a report class period that was currently collecting data from another service class (see Figure 29).

service class index

This index indicates the last service class whose data was collected in the report class period.

Figure 29 illustrates the concept of the mixed-class-indication timestamp in relation to the time interval in which a caller collects workload data.

Figure 29. Mixed-class-indication timestamp in relation to the time interval

A caller invokes IWMRCOLL twice in order to get interval data, first at time t₀ to start the interval and second at time t₁ to end collecting data. With the second invocation at t₁, the caller gets back the mixed-class-indication timestamp. If the returned timestamp is ≥ t₀, as it is for caller 1, it means that transaction data from a different service class started contributing data to the same report class period. The report class is heterogeneous. If the returned timestamp is outside the interval (smaller than t₀), as it is for caller 2, it means that the report class remained homogenous during the calling interval.

Being able to see that a period is homogeneous allows the reporting product to format response time distribution buckets and work manager delay data for this period while it would not report this data for a heterogeneous period. If the timestamp indicates that the report class is heterogeneous, it is recommended to collapse the periods which means to report the data as if the report class had only one period.