Nortel DMS 100 Series Maintenance Manual page 63

Uncontrolled switch of activity
An uncontrolled SWACT can occur when the following events occur: Each of
these states results in a different SWACT plan.
• both units are INSV
• the active unit is INSV and the inactive unit is ISTb
• the active unit is INSV and the inactive unit is SysB
The state of the units and the reason for the activity drop determine the
sequence of events during an uncontrolled SWACT.
If a hardware fault occurs, the system produces a PM181 log. This log can
contain messages that indicate the following:
• activity timeout
• CC links are not present
Message links to the CC or host XPM are broken. Messaging cannot occur
as a result.
• duplicate fault
A critical hardware fault occurred.
• jammed
The unit jams. This message means that the unit cannot change states
(active/inactive).
• ready for ESA
This message is for the RSC-M. In this event, a loss of all CC messaging
occurs. If the original inactive unit does not send a drop message in a time
period, the RSC-M enters ESA.
• static data faults
• The original active unit sends a drop message to the CC.
• The new active unit must send a gain message.
As with controlled SWACTs, the XPM continues to resend the gain message
to a maximum of 15 s.
An uncontrolled SWACT can occur if the original active unit is INSV and the
original inactive unit is ISTb. The critical factor in this example is the
condition that causes the inactive unit to be ISTb. If data synchronization
causes the ISTb, the example is the same for active and inactive units that are
INSV. If data sync causes the ISTb, the original active unit drops sync and the
XPM reinitializes. In this event, the system drops all calls.
DMS-100 Family Remote Switching Center Multi-Access Maintenance Manual XPM11 and up
Maintenance overview 2-47