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Programming WebLogic RMI

# RMI Communication within WebLogic Server

The following sections provide information on how WebLogic RMI using T3 protocol.

- Overview of RMI Communication in WebLogic Server
- Determining Connection Availability

# Overview of RMI Communication in WebLogic Server

RMI communications in WebLogic Server use the T3 protocol, an optimized protocol used to transport data between WebLogic Server and other Java programs, including clients and other WebLogic Servers. 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.

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.

# Determining Connection Availability

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.

Note: It is recommended you do not change the timeout value as it is configured internally.