WARM FAILOVER FEATURE
PERFORMANCE
C - 2
WBPEEUI250016A1
®
into its node without taking time to re-establish exception
report routes.
The backup NPM module must receive a copy of the primary
NPM module database (not exception report data) over the
NKMP01 or NKMP11 cable, before it is ready for warm failover.
The database in the primary NPM module must be stable for 15
seconds before it can be transferred to the backup NPM mod-
ule. After 15 seconds with no changes, the primary NPM mod-
ule transfers (one record at a time) a complete copy of its
database to the backup NPM module. It takes about three min-
utes to completely transfer a large database. If the primary
NPM module database changes before the transfer is complete,
the transfer is aborted and will be restarted after 15 seconds
without database changes. Once the entire database has been
transferred, the backup NPM module is ready for warm
failover. If the primary NPM module database changes after the
backup NPM module is ready for warm failover, the changes
are transferred to the backup NPM module in one of two ways.
If only a few database records have changed, the changes are
immediately transferred to the backup NPM module. If more
than a few database record changes occur in a short time
period, the primary NPM module resets the backup NPM mod-
ule causing the entire database to be transferred to the backup
NPM module.
CPU LEDs on the backup NPM module faceplate indicate the
current state of readiness for warm failover. When the backup
NPM module is initially powered up, LED seven is illuminated.
This state indicates that the backup NPM module is not ready
for warm failover. When the backup NPM module is ready for
warm failover, LED seven goes out and LED eight is illumi-
nated. If the primary NPM module fails before the backup NPM
module is ready for warm failover, a cold failover will take
place. As discussed earlier, cold failover protocol requires that
all exception report routes must be re-established and points
imported from the failed NPM module must be marked with
bad quality until new good quality exception reports are
received.
PERFORMANCE
Performance of the warm failover feature is measured in the
elapsed time between failure of the primary NPM module and
the backup NPM module assuming control. Table
lists the
results of warm failover testing between a redundant process
control unit interface node and a nonredundant process con-
trol unit interface node. The primary NPM module of the
redundant interface node was stopped to simulate failure. The
nonredundant interface node imports exception reports from
and exports exception reports to the redundant interface node.
The time values listed in Table
indicate the time required
for the backup NPM module to recognize a primary NPM mod-
ule failure, for the importing and exporting of various numbers
