A new Guided Walkthrough (GWT) is available below that helps identify and resolve issues relating to agent connectivity problems in System Center 2012 Operations Manager.
An Operations Manager agent is a service that is installed on a computer. The agent collects data, compares sampled data to predefined values, creates alerts and runs responses. A Management Server receives and distributes configurations to agents on monitored computers. Every agent reports to a Management Server in the Management Group. This Management Server is referred to as the agent's primary Management Server.
Agents watch data sources on the monitored computer and collect information according to the configuration that is sent to it from its Management Server. The agent also calculates the health state of the monitored computer and objects on the monitored computer and reports back to the Management Server. When the health state of a monitored object changes or other criteria are met, an alert can be generated from the agent. This lets operators know that something requires attention. By providing health data about the monitored object to the Management Server, the agent provides an up-to-date picture of the health of the device and all the applications that it hosts.
The Operations Manager agent sends alert and discovery data to the primary Management Server, which writes the data to the operational database. The agent also sends events, performance, and state data to the primary Management Server for that agent, which writes the data to the operational and data warehouse databases simultaneously.
The agent sends data according to the schedule parameters for each rule and monitor. For optimized collection rules, data is only transmitted if a sample of a counter differs from the previous sample by a specified tolerance, such as 10%. This helps reduce network traffic and the volume of data stored in the operational database. Additionally, all agents send a packet of data, called a heartbeat, to the Management Server on a regular schedule which is by default every 60 seconds. The purpose of the heartbeat is to validate the availability of the agent and communication between the agent and the management server. For more information on heartbeats, see
How Heartbeats Work in Operations Manager
The article below contains a link to the Guided Walkthrough that will help you solve some of the more common problems with agent connectivity in System Center 2012 Operations Manager: