11g Database Resident Connection Pooling (DRCP)

Oracle 11g has introduced Database Resident Connection Pooling (DRCP) to support server-side connection pooling.  With DRCP, different application processes can share sessions on the same machine and across a multitude of other machines.  This new feature greatly increases the scalability of applications that cannot be deployed as multithreaded, such as PHP applications.  DRCP is also useful in multi-threaded applications that frequently maintain idle connections. 

Unlike some other databases, creating a new connection in Oracle requires a non-trivial amount of database resources.  The Oracle database architecture is designed to create a connection that is capable of performing many concurrent operations using the same connection. Web-tier and middle-tier database applications generally require many threads during their execution.  Each thread must take its turn to consume database resources.  In order to build scalable applications, minimal connections should be used by the application.  In order to support this practice, Oracle has provided connection-pooling options in all of their data access drivers such as OCI and ODP.NET.  The use of connection-pooling in an application allows multiple threads to share resources. This reduces the number of sessions required to support multiple application end users and allows for very scalable applications.

The Growing Need for DRCP

Since its introduction in 1995, PHP has grown to be one of the most popular languages on the web.  Other major database vendors have already taken steps to provide better support for PHP applications.  As the use of this language becomes more common, it is no surprise that Oracle's customers have been eager to use PHP in their web-based applications.  Until Oracle 11g, however, the major obstacle for using PHP to access Oracle databases was the inability of single-threaded PHP to use middle-tier connection pooling.  The PHP architecture was not efficient with Oracle's connection architecture.  Consequently, Oracle users who wanted PHP applications were forced to either use another language or another database.  However, with the introduction of DRCP in Oracle 11g, this is no longer the case. 

Database Resident Connection Pooling provides a connection pool within the database server. The DRCP supports situations where an application requires a database connection for a short amount of time before releasing the connection.  DRCP works by creating a pool of dedicated servers which consist of a server foreground and a database session combined; a model that is referred to as ?pooled? servers. 

Prior to DRCP, only multithreaded applications were eligible to take advantage of the session sharing capability.  By utilizing DRCP, the pooled servers are shared across middle-tier processes on the same host and across different middle-tier hosts.  Additionally, DRCP complements middle-tier connection pools because it eliminates the need to maintain persistent database connections at the middle-tier in order to avoid the overhead of connection creation and termination.