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PNC-DUP (PNC Duplication)
Issue 1 June 2005 1861
Antithrashing and PNC Interchanges
Following a spontaneous PNC interchange, subsequent PNC interchanges are prevented for 5
minutes. This condition is indicated by a y in the Interchange Disabled field of the status PNC
screen. After 5 minutes, the anti-thrashing, timer expires, interchange decisions are re-enabled,
and the field entry is n.
Note:
Note: Should a catastrophic failure occur on the active PNC during the period when
Interchange Disabled? is set to y, there will be no spontaneous PNC
interchange.
Demand PNC interchanges also invoke anti-thrashing, but only for a period of 30 seconds.
During anti-thrashing mode, demand interchanges are also prevented unless the override
option is specified. Use of this option will cause a service disruption.
Repairs on the Standby PNC Components
!
CAUTION:
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 EI.
In this case TDM-CLK 2305 error will be logged, and the clock problem should be
addressed first, if possible.
To repair PNC components in a duplicated PNC:
Most repairs involve fixing a single fault on the standby PNC.
1. Use set pnc lock or busyout pnc to prevent an interchange into the PNC being
repaired.
If a faulty component exists on the currently active PNC, the standby PNC is more severely
faulted. Normally the standby PNC is repaired first because it is the most severely impaired.
2. To repair the active PNC, use reset pnc interchange override-and-lock to
request an interchange and ensure that no subsequent interchange occurs during the repair
of the standby PNC.
The demand interchange may not be necessary if the following conditions drive a
spontaneous interchange:
● The anti-thrashing period from the last interchange has expired.
● The global refresh from releasing the standby PNC has completed.
The standby PNC SOH is better than the active.