Data sources

Installed applications use a data source to obtain connections to a relational database. A data source is analogous to the J2EE Connector Architecture (JCA) connection factory, which provides connectivity to other types of enterprise information systems (EIS).

A data source is associated with a JDBC provider, which supplies the driver implementation classes that are required for JDBC connectivity with your specific vendor database. Application components transact directly with the data source to obtain connection instances to your database. The connection pool that corresponds to each data source provides connection management.

You can create multiple data sources with different settings, and associate them with the same JDBC provider. For example, you might use multiple data sources to access different databases within the same vendor database application. WebSphere Application Server requires JDBC providers to implement one or both of the following data source interfaces, which are defined by Sun Microsystems. These interfaces enable the application to run in a single-phase or two-phase transaction protocol.

ConnectionPoolDataSource - a data source that supports application participation in local and global transactions, excepting two-phase commit transactions.
Note: In two cases, a connection pool data source does support two-phase commit transactions: when the JDBC provider is DB2 for z/OS Local JDBC provider (RRS), or when the data source is making use of participant support. Last participant support enables a single one-phase commit resource to participate in a global
transaction with one or more two-phase commit resources. For more information, consult the article Using one-phase and two-phase commit resources in the same transaction. When a connection pool data source is involved in a global transaction, transaction recovery is not provided by the transaction manager. The application is responsible for providing the backup recovery process if multiple resource managers are involved.
XADataSource - a data source that supports application participation in any single-phase or two-phase transaction environment. When this data source is involved in a global transaction, the WebSphere Application Server transaction manager provides transaction recovery.

In WebSphere Application Server releases prior to version 5.0, the function of data access was provided by a single connection manager (CM) architecture. This connection manager architecture remains available to support J2EE 1.2 applications, but another connection manager architecture is provided, based on the JCA architecture supporting the new J2EE 1.3 application style (also for J2EE 1.4 applications).

These two separate architectures are represented by two types of data sources. To choose the right data source, administrators must understand the nature of their applications, EJB modules, and enterprise beans.

Data source (Version 4.0) - This data source runs under the original CM architecture. Applications using this data source behave as if they were running in Version 4.0.
Data source - This data source uses the JCA standard architecture to provide support for J2EE version 1.3 and 1.4 applications. It runs under the JCA connection manager and the relational resource adapter.

Choice of data source

J2EE 1.2 application - all EJB 1.1 enterprise beans, JDBC applications, or Servlet 2.2 components must use the 4.0 data source.
J2EE 1.3 (and subsequent releases) application -
- EJB 1.1 Module - all EJB 1.x beans must use the 4.0 data source.
- EJB 2.0 (and subsequent releases) Module - enterprise beans that include container-managed persistence (CMP) Version 1.x, 2.0, and beyond must use the new data source.
- JDBC applications and Servlet 2.3+ components - must use the new data source.

Related concepts
Resource adapter
JDBC providers