In Part 1 of this article, I explained the basic steps to move your application from a single server to a scalable solution for both PHP and MySQL. While most Web applications will never need to expand beyond the concepts presented in that article, eventually you may find yourself in a situation where the basic steps aren't enough. Here are some more advanced topics on how you might change your setup to support additional throughput, isolate "concerns" better, and take your scalability to the next level.

He starts with a look at database pooling and how it can not only help you on load balancing your application's resources but also in the caching of the requests. Different resources give different cache results and grouping those together makes life simpler (and faster) for your application. He also talks a a bit about sharding - vertical, manual horizontal and application level techniques.

Here is a screen shot from a PHP OCI8 connection pooling demo that I like to run. It graphically shows how little database host memory is needed when using DRCP connection pooling with Oracle Database 11g. Migrating to DRCP can be as simple as starting the pool and changing the connection string in your PHP application.

He also describes the differences between the pooled and non-pooled connections (to the developer it's as easy as putting ":pooled" in the connect string) in his graphs, and notes that using the pooling doesn't just have to be for large site - smaller sites can benefit too.

One topic that came up yesterday [during Jump In! Camp] was connection pooling and how much difference using pooled connections makes in app performance, so that's what I'll look at in this post.

He starts by defining (from Wikipedia) what connection pooling is and then puts it in the context of SQL Server by talking about the handling of connections returned to the pool. He shows how to enable and disable the feature via a parameter in the connection options and shows how to configure the number of seconds a connection stays active in the pool.

Elton Luís Minetto wrote to tell me that "PHPSC - a PHP user group of Santa Catarina in Brazil - is organizing an event dedicated to PHP that will take place at Chapeco on June 20." [...] He's presenting a session on PHP and Oracle, and will show some great results of using PHP's OCI8 with Oracle 11g connection pooling (DRCP).

The schedule for the event can be found here with details on which talks will be given when (including Elton's at 8am on the 21st.

The whitepaper talks about the changes in the PHP OCI8 1.3 extension, explains some of the concepts behind DRCP and FAN, and gives best practices and tuning tips. It includes a new PHP benchmark which shows up to 20,000 connections being handled by Oracle on commodity hardware using only 2G RAM.

The paper also talks about the FAN support that's built in - the ability for PHP to use the Oracle RAC cluster functionality to make for high availability (switching between nodes). The latest beta with all of this functionality in it can be grabbed from its page on the PECL site.

I've released PECL OCI8 1.3.2 Beta - the latest release of PHP's OCI8 extension with support for Connection Pooling and Fast Application Notification. The release is based on the current PHP 5.3 development branch.

He notes another change in this release - a "session release" bit of functionality persistent connections will do when nothing is referencing them anymore, mking them work a bit more like normal connections. Issues that could be caused by this can be corrected with a new setting (oci8.old_oci_close_semantics) in your php.ini.

Oracle Magazine's May/June 2008 issue contains a "Developer Nation" article. In it, David Kelly interviews Levi Dixon from Community Connect about using PHP and Oracle.

The article references the Oracle/PHP "strange combination" that used to exist and how it's evolved into a vital, living part of Oracle's stack (like with the OCI8 extension).

I've merged connection pooling (DRCP) and Fast Application Notification (FAN) support to PHP 5.3's OCI8 extension. The PHP 5.3 OCI8 code is Beta - in fact, PHP 5.3 itself is still really "Development". (It would be handy to have problems reported before PHP 5.3 goes Production).

He also includes instructions on how to get this new version installed inside of the latest PHP 5.3 snapshot (http://snaps.php.net) to build the new support in.

Oracle & PHP users: make sure you check out the Zend Conference. I'll be given a couple of sessions, "Connection Pooling & Other Features for Data Scaling" and "Performance Tuning for PHP with Oracle Databases". There are plenty of other great talks, too.

There's tons of other sessions happening during the conference including talks on:

• best practices
• enterprise PHP
• the Zend Framework
• API design

Check out the official conference page for information on location, other sessions and registration.

Oracle Database Resident Connection Pooling - a connection pooling feature in the next version of the Oracle DB that will allow very high traffic web sites to scale better. We announced this feature at Oracle OpenWorld in 2006. One cool thing about the feature is that it is not just limited to PHP - any database client could use it.

Luxi talks about pooling in general, pooling database connections specifically, how Oracle handles it and the three views around it - DBA, Client side, and the PHP user views.