Java Flight Recorder is a performance monitoring and profiling tool that records diagnostic information on a continuous basis, making it always available, even in the wake of catastrophic failure such as a system crash.

Java Flight Recorder is available in Oracle HotSpot. When WebLogic Server is configured with HotSpot, Java Flight Recorder is not enabled by default. See Using Java Flight Recorder with Oracle HotSpot in Configuring and Using the Diagnostics Framework for Oracle WebLogic Server, for information about how to enable Java Flight Recorder with WebLogic Server.

If WebLogic Server is configured with Oracle HotSpot, and the Java Flight Recorder is enabled, the Java Flight Recorder data is automatically also captured in the diagnostic image capture. This data can be extracted from the diagnostic image capture and viewed in Java Mission Control. If Java Flight Recorder is not enabled, or if WebLogic Server is configured with a different JVM, the Java Flight Recorder data is not captured in the diagnostics image capture.

The volume of Java Flight Recorder data that is captured can be configured using the Diagnostic Volume attribute in the WebLogic Remote Console, see Configuring WLDF Diagnostic Volume in Configuring and Using the Diagnostics Framework for Oracle WebLogic Server. You can also set the volume using WLST.

In most environments, there is little performance impact when the Diagnostic Volume is set to Low and the most performance impact if Diagnostic Volume is set to High. The volume of diagnostic data produced by WebLogic Server needs to be weighed against potential performance loss.