Capacity planning acknowledges that the business requirements on the system may increase, and forecasts how much resource must be added to the database system to ensure that the user experience continues uninterrupted.

Important sources you’ll add may be CPU power, memory, storage, or network capacity. Planning all this very critical to the success of a project and involves working with management, sysadmins, storage admins, application teams to gather all the requirements for the project.

Keep in mind that cost of the hardware and other resources will high depend on the budget allocated for the project.

Capacity planning is the practice of sizing a system for the needs of the business. From the DBA’s perspective, this means determining what kind and how big of a server and database are needed. The decision will normally be a joint one made by the DBA and SA, and approved by management.

If the system is sized too small, more equipment will be needed just to keep the system going. This is expensive because of the lost performance, time to do an upgrade, and the equipment itself.

If the system is sized too big, its a waste of resources which could be allocated some where else. If the system is sized perfectly for the first year or two, system resource requirements will change over time as the application needs change. It is not as easy a process but proper planning, getting the right information and proper forecasting may ease the process.

Below are some issues to consider:

Disks

This is usually the sysadmin/storage admin’s decision  but generally the more and faster the disks, the better. You will request enough disk space for at least one year of database growth. It is important to multiple disks to spread I/O across.

Memory

The decision on how much memory the server will need will a joint one between the sysadmin and you. The more and faster, the better.

Oracle likes disks, but most of the action takes place in memory.

The amount of memory allocated on the server will also depend a lot on the type and number of databases running from the server.

A rule of thumb is that the total memory allocated to ALL databases which will be running out of the server must NOT EXCEED HALF of the Total memory of the server.

If there is only enough memory for Oracle, other proceses might be continually swapped to disk because of memory shortages, which will affect the entire system.

CPU

The Sysadmin will usually decide on the number of CPU the server will have and usually there will be multiple processors (SMP) on the server.

Oracle will take advantage of multiple processors and it is actually required for some features such as
Parallel Query. Most systems are not CPU bound unless there is bad code running, in which

Operating system

You will have to  check on the oracle website if the version of the operating system, be it Linux or Unix is certified with oracle before the sysadmins build out the server. Oracle provided this information on their support website which you will have access to.

If the OS is not supported for the oracle software installation for the release you want to install, you will have to let the sysadmins know.

Follow the link below to read more about capacity planning