Upgrade Plan Considerations

In an upgrade plan you specify the Java ES components you will upgrade to Release 5 and the sequence by which you will upgrade those components on the different computers or operating system instances in your Java ES deployment.

Your plan will depend on your upgrade objectives and priorities, as well as the scope and complexity of your deployment architecture.

For example, your Java ES deployment architecture might consist of a single Java ES component running on a single computer, and your upgrade objective is to fix some bug in the previous software release. On the other hand, your Java ES deployment architecture might consist of a number of interdependent Java ES components deployed across a number of different computers, and your upgrade objective is to achieve some new functionality by upgrading the minimum number of components required to achieve that end with minimal downtime.

In general, the greater the number of Java ES components and the greater the number of computers in your deployment architecture, the more complex your upgrade plan will be.

However, your upgrade plan will depend on a number of considerations other than the scope and complexity of your deployment architecture. These considerations include the following factors:

• Upgrade Dependencies

• Upgrade All

• Supported Upgrade Paths and Strategies

Upgrade Dependencies

One of the main issues in planning the upgrade of any given Java ES component is that component’s dependencies on other Java ES components. You should evaluate whether such other components also need to be upgraded to support the upgrade of the dependent component.

The two types of upgrade dependencies are:

• Hard upgrade dependency. Upgrade of a product component requires you to upgrade a component upon which it depends. This requirement can be due to new functionality, new interfaces, or bug fixes needed by the dependent component. With a hard upgrade dependency, you cannot successfully upgrade and use the dependent component without first upgrading the component upon which it depends.

• Soft upgrade dependency. Upgrade of a product component does not require you to upgrade the component upon which it depends. With a soft upgrade dependency, you can successfully upgrade and use the dependent component without upgrading the component upon which it depends.

Upgrading a Java ES product component requires you to upgrade all the components upon which it has hard upgrade dependencies, but, with some exceptions noted in this book, allows you to not upgrade components upon which it has soft upgrade dependencies. When multiple interdependent components are involved in an upgrade, you have to upgrade a component if only one of the Java ES components being upgraded has a hard upgrade dependency on that particular component.

In a few special cases, due to incompatibilities that are introduced, upgrade of a component requires you to also upgrade a component that it supports. These special cases are noted in this book.

Upgrade All

• Upgrade All. In this approach you upgrade all deployed Java ES product components to Release 5. In some cases, due to the complexity of a deployment, upgrading an entire system at one time is not feasible for business reasons.

  The two approaches to performing upgrades are compared in the following table:

Table 1–5 Upgrade All

Upgrade Approach	Advantages	Disadvantages
Upgrade All	Maintains a consistent version for all components in your deployed system	Maximizes the number of components to upgrade

The choice between Selective Upgrade and Upgrade All is not rigid. For example, you might choose to selectively upgrade the product components on a particular computer, but wish to upgrade all shared components needed to support the selected product components.In fact, for upgrades from Release 4 to Release 5, selectively upgrading product components, while upgrading all of the corresponding shared components, is often the preferred approach.

Supported Upgrade Paths and Strategies

Your upgrade plan depends on the Java ES release you wish to upgrade to Release 5. Java ES installer only support upgrade from Java ES 2005Q4 (Release 4). The following table describes the different upgrade paths to Release 5, their characteristics, and the upgrade strategies to be used in performing the upgrade.

Table 1–6 Upgrade Paths and Strategies

Release	Java ES Release	System Characteristics	Upgrade Strategies
2005Q4	Release 4	Java ES 5 supports a mixture of Release 4 and Release 5 product components on a single computer.    Interoperability between Release 4 and Release 5 product components has been tested, and known interface incompatibilities are noted in the Sun Java Enterprise System 5 Release Notes for Microsoft Windows.	The coexistence of Release 4 and Release 5 product components provides for the possibility of selectively upgrading Release 4 product components to Release 5 on a single computer or within a deployment architecture consisting of multiple computers.   Release 5 installer automatically installs all required shared components.