RE: How can I get the BBED password?

  • From: "Guerra, Abraham J" <AGUERRA@xxxxxxxxx>
  • To: "Christian Antognini" <Christian.Antognini@xxxxxxxxxxxx>
  • Date: Wed, 13 Apr 2005 13:35:47 -0500

Hello Chris,

I did not know that Oracle actually reorgs a block to pack all the rows
and recover space between rows... That makes sense.

Thanks.

Abraham

-----Original Message-----
From: Christian Antognini [mailto:Christian.Antognini@xxxxxxxxxxxx]=20
Sent: Wednesday, April 13, 2005 10:38 AM
To: Guerra, Abraham J
Cc: oracle-l@xxxxxxxxxxxxx
Subject: RE: How can I get the BBED password?


Abraham

>Well, something that I've noticed with regular dumps is that when you
>update a null column in a record, the whole row is migrated within the
>block to a new location and the space in never reused... I want to use
>bbed to see if that is true...

I agree with you, one of the major problem of regular dumps is that they
are formatted and some information is lost. For this reason, sometimes,
I use BBED to dump the block in hex...

Now, about your problem of free space...

When you update a row and its size is bigger then before, the updated
row is moved at the end of the free space at the top of the block. The
old position become free (it's basically a hole between the rows...).=20
When at the beginning of the block not enough free space is available,
the block is reorganized, i.e. all rows are packet to the end of the
block. Then the updated rows can be placed in the free space at the top.
Of course if the reorganization doesn't help or no holes are available,
the row is migrated to another block. The original block will contain a
simple pointer to the new location and some free space (another hole...)
will be available.


HTH
Chris
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