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Communication Manager Maintenance-Object Repair Procedures
1860 Maintenance Procedures for Avaya Communication Manager 3.0, Media Gateways and Servers
PNC Interchanges
PNC spontaneous interchanges occur when PNC duplication software determines that the SOH
of the standby PNC is better than that of the active PNC. PNC-DUP executes a spontaneous
interchange only when a message from a PNC component MO sends a message indicating that
either a fault has occurred on the active PNC, or a fault has been resolved on the standby PNC
such that the state of health of the active PNC is now lower than that of the standby.
This message will usually indicate the type and location of the failed connectivity component. A
corresponding major or minor alarm is logged by the reporting MO, stimulating an alarm report.
In the less common situation when the resolution of a fault on the standby renders it more
healthy than a simultaneously faulted active PNC, the message will indicate the type and
location of the improved component.
Once the interchange completes, the failed component will be on the standby PNC. A demand
interchange can be requested in the presence or absence of standby PNC faults. The following
sequence of actions can be observed during a fault-free interchange:
1. The Expansion Interfaces currently acting as archangels in the PNs are deactivated as
indicated by the amber LEDs going from flashing to on solid.
2. The EIs in IPSI port networks are interchanged as indicated by the new standby EI amber
LED off and the new active EI amber LED on solid.
3. One by one the EIs in non IPSI port networks are interchanged as indicated by new standby
EI amber LED turning off and the new active EI amber LED flashing (2 seconds on, 200
milliseconds off). At this point the interchange is functionally complete.
4. The SNIs amber LEDs are updated. so that the SNIs on the active SN have amber LEDs
on, while the standby SN’s SNIs amber LEDs turn off.
Certain conditions may interfere with the normal execution of the interchange:
1. In a faulted spontaneous interchange it is possible the PN directly affected by the fault will
be the last to interchange.
2. A user directly affected by the single fault instigating a PNC interchange can experience a
momentary outage of voice path connectivity during the switch.
3. If faults exist on both the standby and active PNC, it is possible to have some PNs go out of
service while others are returned to service.
4. The new standby SNIs amber LED my not be off due to a fault in the line of communication
path to the standby SNIs. In a multi-fault interchange, LEDs on the new active SNIs may not
be on for the same reason.
In any multi-fault situation, use status pnc to determine which is the active PNC.
PNC duplication informs Timing Synchronization maintenance when a PNC interchange has
been completed and indicates which PNC is active. This causes Synchronization to audit and
insure that the primary source for synchronization of Tone-Clocks in each PN is supplied by a
path associated with the active PNC.