Connection Pooling Concepts

Connection Pooling

If you do not use connection pooling, each connection instance (java.sql.Connection or oracle.jdbc.OracleConnection instance) encapsulates its own physical database connection. When you call the close() method of the connection instance, the physical connection itself is closed. This is true whether you obtain the connection instance through the JDBC 2.0 data source facility described under "Data Sources", or through the DriverManager facility described under "Open a Connection to a Database".

With connection pooling, an additional step allows physical database connections to be reused by multiple logical connection instances, which are temporary handles to the physical connection. Use a connection pool data source to return a pooled connection, which is what encapsulates the physical database connection. Then use the pooled connection to return JDBC connection instances (one at a time) that each act as a temporary handle.

Closing a connection instance that was obtained from a pooled connection does not close the physical database connection. It does, however, free the resources of the connection instance, clear the state, close statement objects created from the connection instance, and restore the defaults for the next connection instance that will be created.

To actually close the physical connection, you must invoke the close() method of the pooled connection. This would typically be performed in the middle tier.

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