PHP and Oracle get connection pooling with Database Resident Connection Pooling

9:43am April 25, 2008

One of the major negatives of using Oracle 10g and PHP to build applications is the obvious lack of connection pooling.

Without pooling, frequent connection creation and destruction can be expensive and crippling to high scalability. Oracle's traditional middle-tier connection pools were not applicable to the multi-process PHP architecture. Caching connections within PHP removed connection creation and destruction costs but did not achieve optimal connection resource utilization, incurring unnecessary memory overhead in the database.

Oracle has added Database Resident Connection Pooling (DRCP) as a new feature in Oracle Database 11g. DRCP allows for the sharing of dedicated database server processes across multiple applications running on several hosts. Pooled servers are managed by a connection broker process which pools servers at the database instance level.

With DRCP

Without DRCP

PHP Scalability and High Availability

Dedicated Servers	Shared Servers	Pooled Servers
When the PHP connection is created, a network connection to a dedicated server process and associated session are created	When the PHP connection is created, a network connection to the dispatcher process is established. A session is created in the SGA	When the PHP connection is created, a network connection to the connection broker is established
Activity on a connection is handled by the dedicated server	Each action on a connection goes through the dispatcher, which hands the work to a shared server	Activity on a connection wakes the broker, which hands the network connection to a pooled server. The server then handles subsequent requests directly, just like a dedicated server
Idle PHP connections hold a server process and session resources	Idle PHP connections hold session resources but not a server process	Idle PHP connections hold a server process and session resources
Closing a PHP connection causes the session to be freed and the server process to be terminated	Closing a PHP connection causes the session to be freed	Closing a PHP connection causes the session to be destroyed and the pooled server to be released to the pool. A network connectionto the connection broker is retained
Memory usage is proportional to the number of server processes and sessions. There is one server and one session for each PHP connection	Memory usage is proportional to the sum of the shared servers and sessions. There is one session for each PHP connection	Memory usage is proportional to the number of pooled servers and their sessions. There is one session for each pooled server

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