Wednesday, March 30, 2011

Primary TRANS killed, backup TRANS recovers, but QRY reports lost responses at the end

E.g.:

STATISTICS FOR RATE VARIATION 01:
----------------
      Dialog Statistics:
      ----------
      Dialog initiation Rate.......... = 10 (dialogs/sec)
      Initiated dialogs............... = 300
      Successfully ended dialogs...... = 300
      Failed dialogs.................. = 0
      ...
      Message Statistics:
      ---------
      Total requests sent............. = 19382
      Total responses received........ = 19382
      Total valid responses received.. = 19382
      Total mis-sequenced responses... = 147
      Total lost responses............ = 102
      ...

Lost responses are detected by QRY when seq_num > prev_seq_num + 1. Mis-sequenced responses are detected when seq_num < prev_seq_num. So, the latter occurs because SCOS allows the backup TRANS to handle old dialogs previously initiated by the primary TRANS. And, the former may occur when backup TRANS continue its dialogs afterwards.

As a rule, do not pay too much attention to sequence numbers when SCOS recovers data because this is a rotating U8.