Applications that use container-managed persistence (CMP) beans
normally specify a single database to use with one CMP enterprise
bean. All the CMP enterprise bean instances of one type will read
and write to one database node, which will become the performance
bottleneck. You could deploy the CMP beans N times, once for each
database. However, this is not very flexible for the following reasons:
- Requires N copies of the code with N Java Naming and Directory
Interface (JNDI) names, and so on.
- Requires a deploy step when a database is added.
- It is not easy to manage.
WebSphere® eXtreme Scale has a feature
that allows the application to tell the product which datasource to
use before the transaction starts. When a cluster member receives
a request for a particular application partition, then it communicates
to the CMP runtime to use a specific data source for the duration
of the current transaction. This allows the directed transaction pattern
to be used with the application. Also, such applications can increase
their availability, and it allows the database tier to scale horizontally
on blade type environments. The applications can also take advantage
of the MAPPER table pattern to very flexibly manage data and move
partitions around to better manage the operational aspects of an application,
such as how to move a very busy partition to a lightly loaded database
node for performance reasons.
WebSphere Extended Deployment Version 6.0 supports DB2 UDB and Oracle with the proxy
datasource. The supported Java Database
Connectivity (JDBC) drivers are:
- DB2 legacy CLI-based JDBC
drivers.
- DB2 Universal type 2 JDBC
drivers.
- DB2 Universal type 4 JDBC
drivers.
- Oracle 9i thin client JDBC drivers
See the
WebSphere Application Server Version
6.0.2 document for supported JDBC driver levels. If you need support
for other databases or JDBC drivers, contact IBM support for more details. In
WebSphere Extended Deployment Version 6.0, a new Proxy
DataSource model is offered. The Proxy DataSource model introduced
in
WebSphere Extended Deployment Version 5.1 is renamed
to
5.1 Proxy DataSource in Version 6.0 and is deprecated. Users
are strongly recommended to use the new Proxy DataSource in 6.0. As
a result, the example presented in this section will use only the
6.0 programming model.