Nortel DMS-100 Series Maintenance Manual page 66

1-50 Maintenance overview
3 If the total number of SMBs available for external messages is less than
4 If the total number of SMBs available for external messages is less than
For overload protection, the XLCM holds a reserve of small memory blocks
which are not used to receive external messages. The XLCM holds the
memory blocks to make sure that internal processes have enough small
memory blocks to finish tasks. The XLCM holds the memory blocks even if
the XLCM enters extremely heavy overload. The total number of SMBs
available can be less than or equal to the size of the SMB reserve. In this
event, the system rejects external messages that require SMBs. The system
does not reject maintenance or monitor messages. The XLCM sends an
overload report to the computing module (CM).
The present overload protection system is static because the throttle levels
are constant and not-reactive. The overload protection system also can be
called distributed. The overload protection system is distributed because the
system cannot monitor the overload and initiate and control protective
measures. One place from which these functions can occur is not available.
Early POTS models of the small memory LCM (64k) display the capacity to
be memory block limited. The small memory LCM has 64k. The LCM runs
out of small memory blocks before the LCM runs out of real-time use. The
overall design of the LCM depends on this action. Memory block limited is
an LCM characteristic that carries over to the XLCMs.
297–8351–550 Standard 04.01 August 1999
15, the XLCM stops the transmission of call processing updates to the
mate.
10, the XLCM does not continue to scan the bus interface cards (BIC)
for line scan changes.
XLCM Overload Protection System
Updates to mate unit stopped
XPM delays processing originations
100 Normal Operation
Total available small memory blocks
External messages are not
received
BIC scanning stopped
45 40 35 25 0