Fast Path transaction timings

For each Fast Path transaction, four time intervals are separately calculated.

The following figure shows the boundary events and intervals.

Figure 1. Fast Path transaction event timings
Four intervals. First: input exit routine to GU for message. Second: GU for message to sync point. Third: sync point to router for output. Fourth: router for output to Dequeue output message.

The following list describes the four intervals shown in the previous figure:

  1. Input queue time: reflects the transaction input queuing within the balancing group to distribute the work.
  2. Process time: records the actual elapsed processing time for the individual transaction.
  3. Output queue time: shows the effect of sync point in delaying the output message release until after logging.
  4. Output message time: shows the line and device availability for receiving the output message. If the transaction originated from a programmable controller, the output time could reflect a delay in dequeue caused by the output not being acknowledged until the next input.

The sum of the first three intervals is termed the transit time. This time is slightly different from a response time, because it excludes the line activity for the message, message formatting, and the input edit processing up to the time the message segment leaves the exit routine.