RMI communications in WebLogic Server use the T3 protocol to transport data between WebLogic Server and other Java programs, including clients and other WebLogic Server instances. A server instance keeps track of each Java Virtual Machine (JVM) with which it connects, and creates a single T3 connection to carry all traffic for a JVM. See "Configure T3 protocol" in Oracle WebLogic Server Administration Console Help.
For example, if a Java client accesses an enterprise bean and a JDBC connection pool on WebLogic Server, a single network connection is established between the WebLogic Server JVM and the client JVM. The EJB and JDBC services can be written as if they had sole use of a dedicated network connection because the T3 protocol invisibly multiplexes packets on the single connection.
Any two Java programs with a valid T3 connection—such as two server instances, or a server instance and a Java client—use periodic point-to-point "heartbeats " to announce and determine continued availability. Each end point periodically issues a heartbeat to the peer, and similarly, determines that the peer is still available based on continued receipt of heartbeats from the peer.
The frequency with which a server instance issues heartbeats is determined by the heartbeat interval, which by default is 60 seconds.
The number of missed heartbeats from a peer that a server instance waits before deciding the peer is unavailable is determined by the heartbeat period, which by default, is 4. Hence, each server instance waits up to 240 seconds, or 4 minutes, with no messages—either heartbeats or other communication—from a peer before deciding that the peer is unreachable.
Changing timeout defaults is not recommended.