Pre-Swact And Post-Swact Audits - Nortel DMS-100 Series Maintenance Manual

Pre-SWACT and post-SWACT audits

The SWACT audits provide a mechanism in the XPM that increases
SWACT reliability. The mechanism prevents a SWACT to a mate unit that
cannot maintain activity. If a SWACT occurs and the newly active unit does
not establish two-way communication with the CM, a SWACT back to the
originally active unit is attempted. The new mechanism in the XPM that
provides this additional SWACT reliability is based on the following audits:
pre-SWACT audits
— pre-drop
— pre-gain
post-SWACT audits
— post-drop
— post-gain
The pre-SWACT audit and the post-SWACT audit are present in every unit.
A SWACT involves a drop of activity by one unit and a gain of activity by
the mate unit of a peripheral. Each audit has a different action in the
different states of a SWACT. The audits that control a SWACT within the
XPM are described in more detail in the following sections.
Pre-drop audit
The pre-drop audit accepts a request to drop activity. The pre-drop audit
determines if the mate unit is in a condition to accept activity. The pre-drop
audit runs only in the active XPM unit.
One of two possible sources can initiate a SWACT of the peripheral:
the CM, in the form of a request to the active unit to drop activity
the active XPM unit, which causes an autonomous SWACT
To determine if activity must be dropped, the pre-drop audit evaluates the
following information:
source of the request (CM or XPM)
type of drop request
known status and history of the currently active unit
known status and history of the inactive mate unit
For a CM-initiated SWACT, the SWACT Controller queries the XPM. The
pre-drop audit in the XPM responds to this query. The pre-drop audit
informs the CM if the active unit can comply with a request to drop.
DMS-100 Family SMS Maintenance Manual XPM10 and up
Maintenance overview 1-71