5.1?? That was discontinued YEARS ago.
In any event, the heap size is limited by the JVM its runing on. If its a 32bit, the maximum heap would be 4GB, unless on Windows. In which case a 32bit Windows server would be limited to a maximum of 3GB (theoretical), and a practical limit of 1.5GB.
Kenny Smith
Principal Consultant
IBM Champion
www.strongback.us