Nortel DMS 100 Series Maintenance Manual page 65

RSC-M writes to the location. The error can occur in the program store or
memory store.
• Hard occurs when the RSC-M detects a fault and cannot reread or write to
the memory location.
When a parity fault occurs, the CM determines the action to perform on the
RSC-M unit. This action depends on the state of the unit that reports the fault.
The state of the unit can be active or inactive. The CM handles the three types
of faults.
When the CM detects a parity fault in the active unit of the RSC-M, the CM
sets the unit ISTb. The reason that the CM sets the unit to ISTb is parity. The
CM recovers the unit during a maintenance window. The maintenance
window to recover a parity fault on the active unit is the XPM REX test
window. The time for the XPM REX test window can be the same as the
current time of the switch. If the time is the same, an audit determines if the
active unit of the XPM has an ISTb of parity. If an ISTb is present, the CM
SWACTs and reloads the RSC-M if dependencies are not present. This action
clears the ISTb parity fault and the short term failure (STF) parity fault peg.
This action resolves the parity fault in the RSC-M.
When the active unit reports the parity fault, the system generates a PM181
log. The system generates this log to notify operating company personnel of
the problem. The CM performs the following recovery actions:
• a SWACT of the XPM
• loading the new inactive unit with the XPM software load that the
inventory table that corresponds defines.
The CM considers the loading action an autoload. A manual, CM or mate
reload of the XPM software to the affected unit clears the ISTb.
The CM does not permit an REX test to occur on the following:
• a P-side or C-side node of the XPM that the system recovers from a parity
fault
• the XPM if the system recovers a P-side or C-side node from a parity fault
The CM does not allow two XPMs to perform a parity reload that are in the
same configuration. This condition means a P-side node cannot perform a
parity reload at the same time as the C-side node. A C-side parity reload
cannot occur at the same time as the P-side node. This limit makes sure that
only one XPM in a configuration is in simplex at a time.
The CM informs operating company personnel of a parity fault through
PM181 log reports. This log is the primary trouble indicator. Operating
DMS-100 Family Remote Switching Center Multi-Access Maintenance Manual XPM11 and up
Maintenance overview 2-49