You now have a properly configured and optimized virtual machine for Oracle database server usage. The next step is to tune the guest operating system both for virtualization and Oracle database usage. It is really no different than tuning a stand-alone database server. You need to make sure that you account for correctly setting configuration files, operating system parameters and database parameters as you always have. The only difference is that CPU, memory and I/O assumptions need to be made a little more generically since the hardware has been abstracted and may probably change over time. So the preference is to have all your tuning efforts apply relatively well going forward, when available computing resources may increase.

The only ancillary complexity is that you now may have multiple databases using some shared resources (much like historically hosting multiple databases on a single box) and, therefore, need to account for that at some point in your tuning. But each optimization step should occur in its own due time. Tune the virtual server first (last chapter). Then tune each of the virtual machines as though you are still doing single database per server deployments (which, technically speaking, could occur at some point even in a virtual world). And finally, tune the guest operating system and Oracle database for side effects caused by sharing resources, but do not start here or try to do it all in one pass.

Much like any scientific experiment or database benchmarking, you should only change a single variable per test iteration so that you can properly measure and accord your observed results. I call this technique Incremental Tuning and suggest that it is both the mandatory and only reliable way to correctly optimize any computer system, especially a virtualized one being used for a database.

Optimize by Subsystem

It is best to think of a database server as being composed of four basic subsystems, which should be the focus of any operating system tuning efforts:

• CPU

• Memory

• I/O

• Network

Furthermore, all the above areas should be tuned with the servers purpose in mind hosting an Oracle database. The basic idea is that the overall performance can be no better or worse than the sum of its parts. Plus, all of the above are possibly dynamic in the virtual world, so again making more generic assumptions should generally lead to better aggregate results. This is really nothing more than Incremental Tuning applied at the first granular level of interest: the subsystems.

We will now look at doing just this for both Linux and Windows (note that all these techniques would apply in some fashion to other operating systems such as Sun Solaris, Hewlett Packards HP-UX or IBMs AIX). In all cases, it is assumed that Oracle pre- and post-install steps are being fully and correctly done. So the following are in addition to Oracles default recommendations. A summarization is included at the end of the chapter as well for future quick reference.

This is an excerpt from Oracle on VMWare: Expert tips for database virtualization by Rampant TechPress.