There used to be a general rule of thumb that Oracle on Windows would not support much more than 500 concurrent users. The reason for this rule of thumb was due to the fact that Oracle on Windows did not handle Shared Server connections very well. You will be happy to know that Oracle 9i and Oracle 10g handle Shared Server connections very well. This rule of thumb is not applicable any more.
In today's Oracle environments, the decision to go with Windows or an open source operating like Linux depends more on your company's expertise. If you have Windows administrators but no Linux administrators, then it only makes sense to run Windows. If you have Unix or Linux administrators, but no Windows administrators, then choose Linux.
There are a few other reasons to choose Linux over Windows. Linux servers that do not run a GUI environment typically outperform Windows isntalled on the same hardware. The Windows server has to spend additional overhead supporting the GUI environment, even if no one is directly connected to the operating system. Oracle Corp is also coming out with many tools such as Linux clustering software, which can help you as well.
This was first published in November 2004