How can I determine who has an object locked in the IFS ?

Dear all,
        I ran a RPG call some Java AP include a utility.jar under /java
IFS dircetory. After I the RPG program end normally and I want remove
the /java directory at the same interactive job. I got the
/java/utility.jar object in use error message. So I must signoff and
signon again, then I  can remove that directory. The RPG program
compiled with ACTGRP(*CALLER) under V5R1. My questions as followings:

1. How can I determine who has an object locked in the IFS ?

2. RPG call Java API, processing some operation, finally SETON LR end
normally. Why the JVM still locked the Utility.jar ? How do I end the
JVM after RPG program ended ?

Any help appricated.

Best regards,

Vengoal Chang