Maintenance Manual

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Cisco ICM Enterprise Edition Administrator Guide Release 6.0(0)
Chapter 2 Fault Tolerance
Database Fault Tolerance
Workstations, which switch their active communication paths to the on-line
Logger. At this point, both CallRouters are in service, but only one Logger is
available.
For a single-customer ICM, when the Node Manager detects that the Logger has
gone off-line, it initiates a shutdown and reboot of the machine. In an NSP
environment, the Node Manager does not restart the machine. In this case, manual
intervention is needed to restart the failed Logger.
The Logger’s Node Manager automatically restarts when the machine reboots.
Next, the SQL Server service starts automatically as part of the reboot. SQL
Server automatic recovery runs to ensure that the returning database is consistent
and that all transactions committed before the failure are recorded on disk. Once
automatic recovery is completed, the Logger can then go through the application
synchronization and state transfer process. If configuration data in the on-line
database has changed, the state transfer also updates the configuration data in the
returning database. However, in most cases configuration data will not have
changed during the failure.
Once the two Loggers are returned to synchronized execution, ICM software may
need to recover historical data that was accumulated during the off-line period.
This process, referred to as Recovery, is described in the next section, “Database
Fault Tolerance”.
In a double Logger failure (both Loggers are off-line), the CallRouter continues
to route calls. This is possible because the CallRouter loads configuration data in
its program memory at system initialization. In a double Logger failure scenario,
all messages and data that the CallRouter sends to an off-line Logger are
discarded until a Logger is completely recovered.
Database Fault Tolerance
The Central Controller database provides two major ICM functions:
• Permanent storage of the data that describes a call routing configuration.
• Permanent storage for the historical data that is gathered by the ICM system.
Each time a CallRouter starts, it loads configuration data from the central
database into its program memory. Once the configuration data is loaded, the
CallRouter can begin to route calls (even when the central database is not