Maintenance Manual

Chapter 2 Fault Tolerance
Central Controller
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Cisco ICM Enterprise Edition Administrator Guide Release 6.0(0)
however, because neither Logger is available, data in both databases slowly
becomes out of date. Some reporting functions are not available until the
nodes are returned to service and synchronized execution is restored.
• Both Loggers. In a double Logger failure, call routing continues
uninterrupted. All reporting functions are lost until at least one of the Loggers
returns. Also, you cannot make any configuration changes until at least one
Logger is operational. Such a double failure is extremely rare. The CallRouter
continues to route calls because it has a copy of the call center enterprise
configuration data in its program memory. (The CallRouter loads the
configuration data into memory when it is started and keeps it up-to-date as
configuration changes occur.)
• One Side. If one side of the Central Controller goes off-line, processing
continues uninterrupted. ICM software continues to function as a simplexed
system until the failed side of the Central Controller returns to service. All
functions remain, but the system is running simplexed (without protection
against an additional failure). When the off-line side of the Central Controller
returns, normal duplexed operation is restored.
A double CallRouter failure would temporarily disrupt call routing and reporting
functions. This type of failure is extremely rare (especially in geographically
distributed Central Controller configurations).
Geographic Distribution
To provide maximum protection against disasters such as fires, floods, and
earthquakes, the two sides of the Central Controller can be in separate
locations—even in separate cities. The two Synchronizers communicate with
each other via a private wide area network (WAN) to ensure that they remain
synchronized. This WAN, called the private WAN, is used for no other purpose
than to ensure synchronization between the sides of the Central Controller.
For details on collocated and distributed Central Controller configurations, see
the Cisco ICM Enterprise Edition Installation Guide.