How to start GC logs?

Question

hello
i was reading this article
http://www.jivesoftware.com/jive/entry.jspa?externalID=701
and i wanted to track my GC logs.
we start our jvm using this script. can someone please tell me what arguments would i need to and how i would edit this script to start the JVM in verbose mode or start GC logs
PLATFORM=`/bin/uname`
case $PLATFORM in
  AIX)
    EXTSHM=ON
    LIBPATH="$WAS_LIBPATH":$LIBPATH
    export LIBPATH EXTSHM ;;
  Linux)
    LD_LIBRARY_PATH="$WAS_LIBPATH":$LD_LIBRARY_PATH
    export LD_LIBRARY_PATH ;;
  SunOS)
    LD_LIBRARY_PATH="$WAS_LIBPATH":$LD_LIBRARY_PATH
    export LD_LIBRARY_PATH ;;
  HP-UX)
    SHLIB_PATH="$WAS_LIBPATH":$SHLIB_PATH
    export SHLIB_PATH ;;
esac
"$JAVA_HOME"/bin/java \
  $DEBUG \
  -Dws.ext.dirs="$WAS_EXT_DIRS" \
  -classpath "$WAS_CLASSPATH" \
  -Dwas.install.root="$WAS_HOME" \
  -Dibm.websphere.preload.classes=true \
  $USER_INSTALL_PROP \
  com.ibm.ws.bootstrap.WSLauncher \
  $SHELL "$CONFIG_ROOT" "$WAS_CELL" "$WAS_NODE" "$@"

Answer 1

It's an argument to your java command, so it would be something like:
"$JAVA_HOME"/bin/java \
-XX:-PrintGCDetails \
$DEBUG \
-Dws.ext.dirs="$WAS_EXT_DIRS" \
-classpath "$WAS_CLASSPATH" \
-Dwas.install.root="$WAS_HOME" \
-Dibm.websphere.preload.classes=true \
$USER_INSTALL_PROP \
com.ibm.ws.bootstrap.WSLauncher \
$SHELL "$CONFIG_ROOT" "$WAS_CELL" "$WAS_NODE" "$@"
more details here: http://java.sun.com/javase/technologies/hotspot/vmoptions.jsp
Alper