Re: PCTUSED - when is block added to freelist?

If I understand Jay's question correctly, what he's asking is not how PCTUSED and PCTFREE work, but "what action or actions trigger Oracle to put a block back on the freelist after changing PCTUSED to a higher value?"

Is that correct Jay?

Jared

On Tuesday 03 September 2002 15:38, Miller, Jay wrote:
> I have one huge table (takes up about 30% of the total database storage)
> which has a monthly batch deletion of old data. I had PCTFREE and PCTUSED
> set to the defaults of 10 and 40 respectively.
>
> I occurred to me that I could probably free up a lot more space by
> increasing the PCTUSED so that more blocks would be available to be written
> to (since getting more storage for the server is a bureaucratic nightmare
> here).
>
> So my question is, if I just raise the PCTUSED from 40 to, say, 75 would
> all blocks that fall into the 40-75 range become available for inserts? Or
> is it only after their next update or delete?
>
> Different sections of the docs seem to imply different things. The docs
> say:
>
> A lower PCTUSED reduces processing costs incurred during UPDATE and DELETE
> statements for moving a block to the free list when the block has fallen
> below that percentage of usage.
>
> This seems to imply that it won't be moved to the freelist until a delete
> or update is done that affects that block.
>
>
> But they also say:
>
> A higher PCTUSED increases processing cost during INSERTs and UPDATEs.
>
> This seems to imply that when it's looking to do the insert it might find
> that it can insert to a block.
>
>
> Anyway, why would a lower PCTUSED reduce processing costs during a DELETE
> but a higher PCTUSED wouldn't increase processing costs during a DELETE.
> That makes no sense. I'm befuddled.
>
>
> TIA,
> Jay Miller

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Author: Jared Still
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