Oracle-L: Re: PCTFREE and PCTUSED

From: <Jared.Still_at_radisys.com>
Date: Tue, 04 Nov 2003 15:19:35 -0800
Message-ID: <F001.005D5938.20031104151935@fatcity.com>

Your example block can be 60% full and not be on the free list.

Once your block reaches 90% full, it is removed from the free list.

It will not be put on the free list again until used space in the block falls below PCTUSED, which is 40% in your example.

So, a block fills up, it is removed from the free list, then a couple of rows are deleted and used space falls to 60%. The block is still not on the free list, as the space used has remained above 40%.

Guess what can happen when PCTFREE + PCTUSED = 100?

Not sure what you're reading, but you should be reading the concepts manual, as it explains this all rather well.

HTH Jared

Maryann Atkinson <maryann_30_at_yahoo.com>
Sent by: ml-errors_at_fatcity.com
11/04/2003 03:09 PM
Please respond to ORACLE-L

        To:     Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
        cc: 
        Subject:        PCTFREE and PCTUSED

Suppose I have the following settings which happen to be the defaults as well:

PCTFREE 10
PCTUSED 40 I am trying to figure out what PCTUSED is really used for. My book is telling me that is used so that Oracle knows whether to keep a block in the "free-list".

My point is this: If PCTFREE is 10%, that means the block can be up to 90% full, right?

Well, if the block happens to be 60% full at the moment, then Oracle knows that this block is not full enough because 60 is less than 90, so it can keep it in the free list. I dont see what PCTUSED is needed, it kind of seems I can accomplish the same with just one parm, that being PCTFREE.

But Oracle wouldnt have just put a parm there without any usage, so I guess there's something I dont see...

Any ideas/examples? Any good reasoning anywhere?

Thanks,
maa

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Author: Maryann Atkinson
INET: maryann_30_at_yahoo.com

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INET: Jared.Still_at_radisys.com

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