Use shared classes trace output only for debugging internal problems or for a very detailed trace of activity in the shared classes code.
You enable shared classes trace using the j9shr trace component as a suboption of -Xtrace. See Tracing Java applications and the JVM for details. Five levels of trace are provided, level 1 giving essential initialization and runtime information, up to level 5, which is very detailed.
Shared classes trace output does not include trace from the port layer functions that deal with memory-mapped files, shared memory and shared semaphores. It also does not include trace from the Helper API natives. Port layer trace is enabled using the j9prt trace component and trace for the Helper API natives is enabled using the j9jcl trace component.