Each Java Virtual Machine (JVM) in WebSphere Application Server includes an embedded implementation of Java Management Extensions (JMX). In Application Server, Version 5, the JVMs contain an implementation of the JMX 1.0 specification. In Application Server, Version 6, the JVMs contain an implementation of the JMX 1.2 specification. The JMX 1.0 implementation used in Version 5 is the TMX4J package that IBM Tivoli products supply. The JMX 1.2 specification used in Version 6 is the open source mx4j package. The JMX implementation change across the releases does not affect the behavior of the JMX MBeans in the Application Server. No Application Server administrative application programming interfaces (APIs) are altered due to the change from the JMX V1.0 specification to the JMX V1.2 specification.
The JMX V1.2 specification is backward compatible with the JMX 1.0 specification. However, you might need to migrate custom MBeans that are supplied by products other than the Application Server from Version 5 to Version 6. The primary concern for these custom MBeans is related to the values that are used in key properties of the JMX ObjectName class for the MBean. The open source mx4j implementation more stringently enforces property validation according to the JMX 1.2 specification. Test the custom MBeans that you deployed in Version 5 in Version 6, to ensure compatibility. Full details of the JMX V1.2 specification changes from the JMX V1.0 specification are available in the JMX 1.2 specification.