Tip: Ratio of DS connection pool size to WebContainer thread pool size for WebSphere Portal 6.x
Since, it is possible for a single WebSphere Portal HTTP request to use multiple database connections concurrently, the ratio of the data source connection pool size to the WebContainer Thread Pool needs to be tuned.
For the WebSphere Portal databases, the recommended ratio is 2:1.
For Workplace Web Content Management (JCR) database, the recommended ratio is 2.5:1.
For example, if the WebContainer thread pool maximum is 50, then each WebSphere Portal data source connection pool maximum should be 100 and the JCR data source connection pool maximum should be 125.
Verify that your database server is able to handle all incoming client connections from all WebSphere Portal cluster member(s).
Check out the Tech Note here.