334 IBM Tivoli Monitoring: Implementation and Performance Optimization for Large Scale Environments
10.1.1 Hub monitoring server availability
The hub monitoring server is the heart of the monitoring environment. It has to be
treated differently than the remote monitoring server components. The hub
monitoring server contains the internal monitoring database, called the
Enterprise Information Base (EIB). The EIB contains the definitions of objects,
such as the information about managed systems, situations, policies and
definitions for historical data collection. It is the most critical component in the
whole environment.
Although policies used for automation runs on the hub monitoring server
independently, only a part of the situations run on the hub monitoring server.
Situations regarding EIB objects and correlated situations across multiple
managed systems run on the hub monitoring server. The situations on the
agents, if deployed, run independent of the hub monitoring server. If the hub
monitoring server fails, an agent cannot forward situation event notifications, but
the situation
actions will continue to run.
An agent can restart its own monitoring server via a restart action within the
situation running on the agent. The notification might be lost, however, because
the situations raised while the hub was down will be lost, unless they are still true
at the agent when they are restarted as part of the reconnection behavior.
The Warehouse Proxy agent and the Summarization and Pruning agent will work
independently, because the instructions are stored at the agent level.
Hub monitoring server monitoring
Basically, if you use a portal, you will see an error message box when the hub
monitoring server is not available, as shown in Figure 10-2 on page 335.
Important: A remote monitoring server also has an EIB, but with different
content. The hub EIB contains the
full content for the entire environment. The
remote monitoring server EIB only contain information for the agent that it
takes care of.
Also, the remote monitoring server EIB state (for example, situation status) is
more volatile, in that it is rebuilt every time the remote monitoring server
reconnects to a hub.
Tip: If the agent is reporting to a remote monitoring server, the agent can still
report situations to its remote monitoring server, even though the hub fails.
This data will later be lost when the remote monitoring server reconnects to
the hub and cleans its current situation status cache.

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