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Chris Saxon

Thanks for the question, Nikhil.

Asked: November 03, 2016 - 9:01 am UTC

Last updated: November 03, 2016 - 3:47 pm UTC

Version: 11g

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You Asked

Hi Team,

Can i get any reference on -
1. What is the Difference between Rebuild Index & Gather Index Stats.
2. When to go for Rebuild Index or Gather Index Stats


and Chris said...

Index rebuilds and gathering stats are completely separate things!

- Rebuilding an index re-creates it
- Gathering stats gets information about the values it references. e.g. How many values there are, number of different values, etc.

There aren't cases where you'd pick between them.

Rebuilding should happen "almost never":

Normally you wouldn't gather index stats as a standalone process either. Most of the time you'll gather the table stats and do the indexes on it at the same time.

The stats gathering job does this when the table data is "stale". i.e. when the number of changes to the table exceed a certain threshold. In most cases you can use the default (10%). But you may want to tweak this if it isn't working for you.

If you want to know more about this, check out Richard Foote's articles on index stats:

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