RE: Ghost Data
- From: "Matthew Zito" <mzito@xxxxxxxxxxx>
- To: <Brandon.Allen@xxxxxxxxxxx>, <michaelw436@xxxxxxxxx>, "oracle-l" <oracle-l@xxxxxxxxxxxxx>
- Date: Tue, 30 Jun 2009 19:13:36 -0400
I'm sure someone else will actually *know* the answer, but I'll hazard a guess.
I suspect that you're right, that it just grabs a full block worth of data
from memory, before it writes it out. Perhaps they think it's better to do
that than to write an unaligned block?
Matt
--
Matthew Zito
Chief Scientist
GridApp Systems
P: 646-452-4090
mzito@xxxxxxxxxxx
http://www.gridapp.com
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx on behalf of Allen, Brandon
Sent: Tue 6/30/2009 6:41 PM
To: michaelw436@xxxxxxxxx; oracle-l
Subject: Ghost Data
I'm starting a new thread on this specific topic to avoid high jacking the
other one. Reading about this "ghost data" reminds me of a surprising
discovery I made a few months ago but had forgotten about until today.
I created a brand new tablespace with a new datafile, created one table in the
new tablespace and inserted one row. When I ran "strings" on the datafile, I
only saw the instance name and tablespace name - so far, so good. Then I
forced a checkpoint to write the data out to the file and was surprised to find
that when I looked at the datafile with "strings" again, it had a bunch of data
from other database tables in it.
Is this normal, known behavior? Does Oracle just copy data from other blocks
of the database into the new file as buffer space to fill it up? I duplicated
this on 8.1.7.3 and 10.2.0.4.
Thanks,
Brandon
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On
Behalf Of Michael Wehrle
Sent: Tuesday, June 30, 2009 1:45 PM
To: Mathias Magnusson; oracle-l
Subject: Re: Quickest Way To Recreate a Database
Mathias, Oracle explains what this ghost data is here...
http://www.oracle.com/technology/deploy/security/database-security/transparent-data-encryption/tde_faq.html#A15032
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