Re: PCTFREE

From: Brian Peasland <peasland_at_edcmail.cr.usgs.gov>
Date: Thu, 9 Dec 1999 14:03:58 GMT
Message-ID: <384FB6CE.D369749D@edcmail.cr.usgs.gov>

If PCTFREE is high,
  Advantages: More space for updating rows in the block.

                 Reduces row migration.

  Disadvantages: Wastes space in block.

If PCTFREE is low,
  Advantages: Better use of space in block.   Disadvantages: Increases row migration (reduces performance)

If your typical row of data in the table will require updating (and this causes the row length to increase), then a higher PCTFREE is in order. If your typical row of data in the table does not require updating, then a lower PCTFREE is in order.

HTH,
Brian

John Chiu wrote:
>
> Yann Ming <ylew_at_my.lhsgroup.com> wrote in message
> news:384f24d3_at_news.lhsgroup.com...
> > Hope someone could help me on this.
> >
> > What is PCTFREE?
>
> PCTFREE defines the percentage of free space in a database block when you
> allocate a database block in your table/index.
>
> > How would the PCTFREE size impact on the database performance?
>
> allow the database row to expand in the future.
>
> > How would I know what is the best size for PCTFREE?
> >
>
> no definite answer. It depends on the application/nature of your
> table/index.
>
> HTH
>
> John Chiu
Received on Thu Dec 09 1999 - 08:03:58 CST