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Rebuild Index

Former Member
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Hi

I am deleting data from table DBTABLOG which is occupying 100GB of space, due to the scheduled job I expect 96GB of data to be deleted from this table.

Will this 96GB be available as free space, the index table occupies about 40gb of data, do I need to regenerate the index for this table to get the space for use

please guide me

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Answers (1)

former_member204746
Active Contributor
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in theory, an index rebuild is not necessary. But in your case, I highly recommend building your indexes for this table. you will gain 96GB of data and about 38GB of index space.

do not forget to recalc DB stats after reorg.

Former Member
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Hello Eric

Is a re-org necessary every time to get back the unallocated space after I delete records from a table. If yes, please let me know what is the time estimated to do an online re-org, i know that it is dependent on hardware but can you please tell me the approximate time it generally takes for performing re-organization of say 100GB.

stefan_koehler
Active Contributor
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Hello Grame,

> Is a re-org necessary every time to get back the unallocated space after I delete records from a table

Yes, if you want to use this space by another database object (for example another index or table).

No, if you want to use this space again by the same object.

As you already said it really depends a lot on the hardware and the way you rebuild the index (ONLINE / OFFLINE / PARALLEL). You can check the metalink note #278600.1 for more information about the access pathes by an index rebuild.

I have rebuilt some indexes ONLINE with round about 100 GB on a good server with SAN disks. It takes round about 4 - 4.5 hours.

Regards

Stefan

former_member204746
Active Contributor
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your index reorg will be fast because you only have 4GB of data. expect less than 10 minutes for that.

Former Member
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Thanks for the replies...