"Messages Suppressed" in SNA Server Level 2 Tracing.

SUMMARY

The output of an SNA Server level 2 trace may include the following line:

   ...
   |000000a5.000000a1 SDLC   --------------------------------08:17:36.79
   |000000a5.000000a1 SDLC   ***** 63965  messages suppressed ****
   ...
				

This indicates that the message that is passing between the SNA Server Link service and the actual driver is the same as the message that was just logged in the trace file. The message suppressing function was added to level 2 tracing to keep SDLC trace files manageable and not let them get too large. It uses the following algorithm:

1. Each time the trace code is asked to trace an SDLC message, it compares it with the two previous messages that it received.
2. If either message matches, it increments the count of messages suppressed, traces nothing, and updates the buffer of the last two messages received.
3. If there is no match, it checks to see if it was suppressing messages. If it was, it traces the XXXX messages suppressed line, then traces the message and updates the buffer of the last two messages received.

By doing this, an active SDLC line which has the following activity:

   Tx RR
   Rx RR
   Tx RR
   Rx RR
   Tx RR
   Rx RR
   ...
				

will only take 3 lines in a trace file, no matter how many times the same message repeats. The result, in a simple form, will look like the following:

   Tx RR
   Rx RR
   X messages suppressed.