The member resource adapters connected to each database node and the root resource adapter that bundles these multiple member resource adapters together configure a clustered connection pool. A description of the root resource adapter and member resource adapter is as follows:

• Root resource adapter
  This resource adapter is accessed from the J2EE applications when a clustered connection pool (connection pool clustering) is used. The root resource adapter bundles the member resource adapters together. With the root resource adapter, the processing requests to the root resource adapter are distributed to the member resource adapters. Note that the root resource adapter does not have a connection pool.
  
• Member resource adapter
  This resource adapter is connected to clustered individual database nodes. A member resource adapter is necessarily accessed via the root resource adapter. The connection pool of a member resource adapter is called a member connection pool.
  

The following figure shows the flow of processing for obtaining a connection when the connection pool is clustered.

Figure 3-63 Flow of processing for obtaining a connection

1. The J2EE application makes a connection request to the root resource adapter.
2. The root resource adapter selects one member connection pool and sends the connection request.
3. A connection is selected from the member connection pool and returned to the J2EE application.

The database that can use the connection pool clustering functionality is Oracle11g only when the RAC functionality is used. The available JDBC driver is Oracle JDBC Thin Driver.

The following table describes the J2EE components and functionality available for database connections when the connection pool clustering functionality is used.

Table 3-73 J2EE components and functionality available for database connections (Connection pool clustering functionality)

Items		Oracle11g (when the connection pool clustering functionality is used)
J2EE components	Servlet/JSP	Y
	Stateless Session Bean	Y
	Stateful Session Bean	Y
	Singleton Session Bean	Y
	Entity Bean (BMP)	Y
	Entity Bean (CMP 1.1)	N
	Entity Bean (CMP 2.0)	N
	Message-driven Bean	N
Available functionality	Connection pooling	Y
	Connection pool warming up	Y
	Displaying the connection pool information (cjlistpool command)	Y
	Clearing the connection pool	Y
	Connection test for resources	Y
	Detecting the connection errors	Y
	Statement pooling	Y
	Statement cancellation	Y#
	Statement setQueryTimeout method	Y#
	PRF trace output for the connection ID	Y
	Output of the SQL statement for troubleshooting	Y

Legend:

Y: Available

N: Not available

# Precautions need to be taken when you connect to Oracle. For details, see 3.6.6 Preconditions and notes on connecting to Oracle.

Note

To use a resource adapter, you must resolve the references from the J2EE application to the resource adapter. When you customize a J2EE application that uses the resource adapters, resolve the references from the J2EE application to the resource adapter.

For details on the functionality available with the root resource adapter and member resource adapter, see 3.3.4 Resource adapter functionality.