A Java ES release family consists of a feature release and its associated maintenance release as illustrated in the following figure.
A Java ES feature release initiates a release family, and a number of subsequent maintenance releases (called Java ES update releases) provide distributions that periodically consolidate intervening component update and point-fix releases. These individual component maintenance releases are independently collected in a Java ES accumulated patch cluster.
The maintenance aspect of the Java ES release model is represented by both the Java ES update release and the Java ES accumulated patch cluster, described as follows:
Java ES Update release. The maintenance aspect of the Java ES release model is represented by both the Java ES update release and the Java ES accumulated patch cluster, described as follows:
As compared to a feature release, an update release contains fewer, smaller, and/or lower risk features. Other than in rare exceptions, an update release is 100% backwardly compatible with the release family with which it is associated.
Java ES 5 Update 1 is a Java ES update release.
Accumulated patch cluster. The accumulated patch cluster contains the latest set of individual component point-fix and update releases for the components in a release family. It facilitates upgrade to the most recent versions of all Java ES components.
The accumulated patch cluster is established at the onset of a release family and has a life cycle corresponding to the support life of the release family. It is updated whenever a new component point fix or update release is made available. Other than in rare exceptions, the accumulated patch cluster is 100% backwardly compatible with earlier releases in its release family.
The significance of the Java ES release model, from an upgrade point of view, is that an upgrade from one Java ES release family to another (a feature upgrade) involves significant impact and risk, and requires a more complex upgrade plan, as compared to an upgrade within a release family (a maintenance upgrade).