Websphere JNDI resource scoping

Most folks have their application deployed at cluster level and so the resources attached to them such as Database, JMS, etc., I was challenged by my websphere administrator the need to create database resources at cluster level when applications created at different clusters talk to same database. My initial hunch was these resources are isolated under cluster and therefore will not have resource contention, however when they are moved to cell level their isolation is lost and resources will now be shared by all application clusters.

Interestingly this wasn't true. Even though IBM marks resources created at cell level with broader scope, when it comes to connections each node gets its own share. Despite the scope of a defined resource, the resource properties apply at an individual server level only.The application scope has precedence over all the scopes.

• The server scope has precedence over the node and cell scopes.
• The node scope has precedence over the cell scope.

For example, if you define the scope of a data source at the cell level, all the users in that cell can look up and use that data source, which is unique within that cell. However, resource property settings are local to each server in the cell. For example, if you define the maximum connections as 10, then each server in that cell can have 10 connections.

The cell scope is the most general scope and does not override any other scope. The recommendation is that you generally specify a more specific scope than the cell scope. When you define a resource at a more specific scope, you provide greater isolation for the resource. When you define a resource at a more general scope, you provide less isolation. Greater exposure to cross-application conflicts occur for a resource that you define at a more general scope.