Selecting work for output service writers

JES3 uses the “best fit” approach to match SYSOUT data sets with an available device (writer). The following paragraphs describe the “best fit” approach.

Once the best fitting data set is determined, the remainder of that job's data sets are processed applying the “best fit” approach within the boundary of the same job.

Secondly, if the operator does not specify one or more of the possible writer-selection criteria, JES3 does not take any action with regards to that characteristic (such as issue mount messages or load CHAR arrangements). JES3 does not verify that the output data characteristics match that of the writer, nor that a mount message is issued for changes in writer set up. This can result in a job that requires special forms printing on the wrong form if you omit forms as a selection criterion.

Thirdly, JES3 establishes the writer-selection criteria during JES3 initialization by the WS= parameters on the OUTSERV and DEVICE initialization statements. The writer-selection criteria can be modified using the writer DSP commands: *CALL, *RESTART, and *START with the WS= keyword. The values specified on the most recent command are placed at the front of the current selection list. Similarly, values specified on the DEVICE initialization statement are placed at the front of the selection list, derived from the OUTSERV statement.

An output service writer has characteristics that can be changed (changeable characteristics) or cannot be changed (non-changeable characteristics) during work selection processing. Some of the writer's characteristics can be toggled between changeable and non-changeable by using the hold option for that particular characteristic. Non-changeable characteristics listed in the writer-selection criteria require the data set to match the device characteristics; otherwise the data set is considered ineligible.

Changeable characteristics allow a writer to make adjustments to the writer-selection criteria list to accommodate data sets with different characteristics than are currently in use on the device. Table 1 illustrates the special considerations you should take when changeable characteristics are involved in writer selection processing. Note that priority always plays a role in work selection. Column “WS=” defines the writer-selection criteria considered in each example. Column “Behaviors” describes the result of the selection algorithm based on the first two columns. Included in this column will be the “perfect fit” case followed by the next “best fitting” cases, if applicable.