As defined in the Sun JDBC 2.0 Standard Extension specification,
data sources allow you to manage a pool of connections to a database. Using
connection pools provides you with the following advantages:
- It improves performance. Creating connections is expensive; a data source
creates a connection as soon as it is instantiated.
- It simplifies resource allocation. Resources are only allocated from the
data sources, and not at arbitrary places in the code.
- It simplifies connection calls. To get a connection in JDBC 1.0, you would
need to call Class.forName() on the class name of the database driver, before
making DriverManager calls.
Data sources work as follows:
- When a servlet, or other client, wants to use a connection, it looks up
a data source by name from a JNDI server.
- The data source then returns a connection to the client.
- If the data source has no more connections, it may ask the database manager
for more connections (as long as it has not exceeded the maximum number of
connections).
- When the client has finished with the connection, it closes the connection.
- The data source then returns the connection to the available pool.
You can configure data sources for WebSphere® Application Server v6.0
by using the Deployment page in the application deployment descriptor editor
or using the administrative console. For WebSphere® v5.x1 test environments and servers you can configure data
sources by using the Data Source page in the server editor.