Enabling Verbose GC

Use these panels - Application servers > ClstAppSrv01 > Process definition > Java Virtual Machine, then, check the following

Verbose garbage collection 

Of course, you can always use wsadmin 

AdminTask.setJVMProperties('[-nodeName D-F-02Node01 -serverName ClstAppSrv01 -verboseModeClass false -verboseModeGarbageCollection true -verboseModeJNI false -runHProf false -hprofArguments -debugMode false -debugArgs" -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=7777" -executableJarFileName -genericJvmArguments -disableJIT false]')