Avaya S8700 Maintenance Manual page 971

ATM PNC-DUP (ATM PNC Duplication)
Antithrashing and PNC Interchanges
Following a spontaneous PNC interchange, subsequent PNC interchanges are
prevented for 5 minutes. This condition is indicated by y in the Interchange
Disabled? field of the status pnc form. After 5 minutes, the antithrashing, timer
expires, interchange decisions are re-enabled, and the field displays n.
NOTE:
Should a catastrophic failure occur on the active PNC during the period
when the Interchange Disabled? field is set to "yes," there will be no
spontaneous PNC interchange.
Demand PNC interchanges also invoke anti-thrashing, but only for a period of 30
seconds. During antithrashing mode, demand interchanges are also prevented
unless the override option is specified.
!
CAUTION:
Use of this option may cause a service disruption.
Repairs on the Standby PNC Components
!
CAUTION:
If there is a TDM-CLK alarm, system timing may be routed through part of
the standby PNC, and circuit switched data may be affected by the following
repair procedures. This can happen, for example, when a slave tone/clock
circuit pack experiences a loss of signal and switches to receive timing from
the standby ATM-EI. In this case TDM-CLK 2305 error is logged, and the
clock problem should be addressed first, if possible.
To repair PNC components in a duplicated PNC proceed as follows:
1. Most repairs involve fixing a single fault on the standby PNC. Use set pnc
lock or busy-out pnc to prevent an interchange into the PNC being
repaired.
2. If a faulty component exists on the active PNC, this also means that the
standby PNC is more severely faulted. Normally, the standby PNC is
repaired first, since it is the most severely impaired.
To repair the active PNC (standby is already repaired), issue the set pnc
unlock command, which generates a spontaneous interchange. In a PNC
demand interchange with reset pnc interchange use the
override-and-lock qualifier for the active PNC. The override-and-lock
option ensures that no subsequent interchange can occur during the repair
of the standby PNC. A demand interchange may not be necessary if the
following conditions drive a spontaneous interchange:
At this point, the faulty component is on the standby PNC, and the PNCs
are locked in their current active/standby state.
555-233-143
The anti-thrashing period from the last interchange has expired.
The global refresh from releasing the standby PNC has completed.
The standby PNC's state of health surpasses the active PNC's.
Issue 1 May 2002 8-249