Nortel DMS-100 Series Maintenance Manual page 54

1-38 Maintenance overview
The SWACT controller polls data in the XPM to determine if the inactive
unit can maintain activity. The XPM communicates to the SWACT
controller query if the active unit can comply with the request to drop
activity. State data determines if the active unit can or cannot drop activity.
For more information about XPM state data, refer to the section on Pre-gain
audit in this document.
Pre-SWACT and post-SWACT audits
Feature AN0538, SMS Pre-SWACT/Post-SWACT Audit, improves the
warm SWACT operation. Feature AN0538 denies the SWACT if the
inactive unit cannot maintain activity or communication with the CC. Under
these conditions, feature AN0538 can SWACT-back to the original active
unit. The software that drives this feature is the SWACT controller in the
CC with an autonomous ability in the SMS software.
Pre-SWACT audit
Before the active system initiates a SWACT, the active SMS unit queries the
mate SMS unit over the intermodule communication (IMC) links. The
active SMS unit messages the SWACT controller in the CC. Feature
AN0538 improves the pre-SWACT audit of the inactive unit to include the
state of the unit during diagnostics. Feature AN0538 assigns a weighted
value to the results of the diagnostics. The pre-SWACT audit query results
in a boolean pass or fail.
If the SWACT controller denies a manual request for a warm SWACT, the
MAP terminal provides information on the denied request. The MAP
terminal provides a detailed reason for the denial. The MAP terminal
informs you that you can enter the SWACT FORCE command to override
the SWACT controller. If you override the SWACT controller, the system
attempts a warm SWACT. The system does not consult diagnostic history or
state.
Post-SWACT audit
After a SWACT, the inactive unit can become system busy and return to
service if the following two events occur:
The earlier active unit remains in service until the new active unit can verify
two-way communication with the CC. The new active unit verifies that the
unit can maintain activity. Communication can fail and the new active unit
cannot maintain activity always. If one of these events occurs the SMS
initiates a SWACT-back to the original active unit.
297-8231-550 Standard 09.01 August 1998
two-way communication is available with the CC
the new active unit can maintain activity