Takeover Capability - Nortel DMS-100 Series Maintenance Manual

than entrance criteria at each level). Overload is detected by measuring the
number of times the size of the message queue exceeded a specific value
during the measurement period, which is 20 seconds.
The threshold value for number of messages on the queue, and for the
number of times the queue exceeded that number is defined by four values,
which are:
LOW_ENTRY_THRESHOLD
LOW_EXIT_THRESHOLD
HIGH_ENTRY_THRESHOLD
HIGH_EXIT_THRESHOLD
Each of the four threshold values are used first to compare the number of
messages on the task queue each time the procedure, SEND_MSG, is called.
Secondly, if the number of messages on the queue is above the value for
LOW_ENTRY_THRESHOLD, a counter called OVLD_LEVEL is
incremented. At each 20 second interval, the value of OVLD_LEVEL is
compared to the LOW_ENTRY_THRESHOLD and
HIGH_ENTRY_THRESHOLD values to determine if a new overload state
has been entered. If a task is already in overload, the OVLD_LEVEL
counter is compared to exit thresholds to determine if the current overload
state has expired.
Overload control
Overload control is made up of overload messages to the CM and traffic
throttle messages to the LTC+.
At LOW overload, a message is sent to the CM, which marks the unit
Inservice trouble (ISTb), and blocks maintenance actions on the unit; call
processing traffic is not affected. At HIGH overload, a message is sent to
the LTC+ to throttle fifty per cent (50%), of both originations and
termination to the RLCM-EDC unit. The overload condition at the CM will
remain in effect until another message is sent to drop overload state.
However, the LTC+ requires a new overload message to be sent at least
every three seconds to keep the throttling in effect. If the LTC+ is not
refreshed, it will incrementally drop out of overload in the space of about
fifteen seconds. This is to prevent a lost message keeping the LCM throttled
indefinitely.

Takeover capability

Because there are power connections between the two shelves of the LCM,
the LCM can operate in a load-sharing mode. If one power converter goes
out, the mate converter supplies power to both shelves. This is called
Maintenance overview 1-59
DMS-100 Family Maintenance Manual ABSK007