How long would take to upgrade an Oracle DB which has 1T data from 10g to 11g usually/roughly? I need to estimate the down time for it since it is a prod db. Thanks much!
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30-90 minutes according to Oracle's Best Practices for Upgrading. This is about the closest estimate you will get given all the unknowns in this situation.
The size of the database really matters very little in determining how long the upgrade will take. Here are the main factors effecting the duration (from the Oracle.com upgrade blog):
Here are some additional factors you may want to consider that aren't related to the core of the upgrade itself:
Probably the biggest factor effecting the upgrade is the unknown factor. Even when the upgrade is practiced in advance on similar hardware with similar data sets, etc. things can still occur that were unanticipated and can drastically effect the duration. With that in mind you should mimic the production environment as closely as you can for the test upgrades. That is, as close as your budget will allow.
If space is the issue preventing you from testing the upgrade, consider restoring the database to a test box excluding some of the larger user tablespaces. This won't give you an exact feel for the time, but it should give you a closer ballpark and allow you to work through more of the unknowns.
Presumably, you have a development and test instance of this database running on similar hardware with a similar data volume and the same database components installed, correct? And, presumably, you will be upgrading these lower environments (and testing that whatever applications use this database still function correctly), correct?
Assuming that is the case, I'd time how long it took to upgrade the development database and use that as your estimate of the time required to upgrade the other instances. There are, obviously, a number of factors that determine how long the actual upgrade will take. My guess is that the downtime would likely only need to be an hour or two but you're much better off using the actual time required to upgrade dev.
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