A common but difficult problem to diagnose is one where the wrong JVM version or level was started. You can easily spot this problem if you start the JVM with the -showversion option. If you ran the following command on an IBM® JVM on Linux:
> java -showversion <class name>
the following output is seen in your application log:
java version "1.7.0"
Java(TM) SE Runtime Environment (build pap6460sr7ifix-20100220_01(
SR7+IZ70326))
IBM J9 VM (build 2.4, JRE 1.7.0 IBM J9 2.4 AIX ppc64-64 jvmap6460
sr7-20100219_54049 (JIT enabled, AOT enabled)
J9VM - 20100219_054049
JIT - r9_20091123_13891
GC - 20100216_AA)
JCL - 20091202_01
We recommend setting the -showversion option for all JVMs. This simple and inexpensive step provides valuable information that can help ensure that the correct JVM version and mode are used.