Re: Disk capacity planning

Hi Rhojel,

You've had some responses that go beyond your forecasting question. I'll go the simple-minded route here. Maybe there is some canned software out there that will do it but it seems vendors stay away from forecasting future growth. Maybe this is to avoid being held accountable for "faulty" results (probably shouldn't trust my answer either...). Anyway, I was taught that the first rule of forecasting is that the forecast will be wrong. This doesn't mean you shouldn't forecast the growth of your database. It just means that you need to follow your forecast on a regular basis and note variances (ie: significant changes to growth rates) and ask questions. A spike in growth can be a development boo-boo, new functionality, growth in business, or something else.

A simple approach is to track (at least monthly...depending on your comfort zone) the physical size of tablespaces and actual data and calculate net changes in size between your forecasting periods (eg: Month). Summarize this and calculate the average rate over time (eg: Year). Given the average rate and the last rate, you can forecast your growth using both rates over some horizon (1 year? 2 years?) and compare it to your available diskspace. You should be able to identify when you'll run out...but don't assume this will be correct. Also track significant events that may have driven growth. And if there is a major difference between the average growth rate and the last growth rate...it's analysis time.

There are fancier forecasting methods like "exponential smoothing" and so on but the simple approach might get you started. But you need to keep testing results to see if your situation has changed. The above would be a fairly simple spreadsheet.

Kip Bryant

|Hi everyone!

|Can anybody point me to any good documentation regarding disk capacity
|planning? Sharing your experience or approach will also give me so much
|help. I'd like to know other people's approach on forecasting the growth
|of their databases particularly on determining the (growth) rate of disk
|space usage and on deciding when to add and how many disk to add on an
|Oracle server.

|Thanks in advance.

|Best Regards,
|Rhojel

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