See Note: 1029850.6 on MetaLink for more details but here is algorithm used
for freelist
A block is put on
free list if
the free space in
the block is
greater than the
space reserved by
PCTFREE.
Blocks linked in a
free list are
available for
future updates or
inserts.
A block is unlinked
from a free
list if the free
space in the
block is not
enough to allow a
new row
insert, and if the
percentage of
the used space
remains above
PCTUSED.
A block is relinked
to a free
list if after
DELETE or UPDATE
operations, the
percentage of the
used space
falls below
PCTUSED.
Each time a block
is added to a
free list, it is
linked at the
head of the
chain.
Rick
"Miller, Jay"
<JayMiller@TDWater To: Multiple recipients of list
ORACLE-L <[EMAIL PROTECTED]>
house.com> cc:
Sent by: Subject: RE: PCTUSED - when is block
added to freelist?
[EMAIL PROTECTED]
09/04/2002 11:03
AM
Please respond to
ORACLE-L
Yes, that's what I intended to ask :).
Thanks, Jared.
Jay
-----Original Message-----
Sent: Tuesday, September 03, 2002 9:18 PM
To: Multiple recipients of list ORACLE-L
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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