It all depends which words you use -- sorry for the ambiguity...
As Cary replied earlier, EXP just queries sys.seg$ (i.e. DBA_SEGMENTS) to
find the bytes and uses that for the newly-calculated INITIAL. This can be
seen in a SQL Trace initiated on the EXP's server process...
----- Original Message -----
To: "Multiple recipients of list ORACLE-L" <[EMAIL PROTECTED]>
Sent: Thursday, May 16, 2002 10:48 AM
Tim,
I may be wrong but I thought that compress=y just adds up the total space
allocation from SEG$ rather than calculating them from storage parameters. I
know this is a trivial point but I'd appreciate the info if it sets about
things differently.
regards,
Mike Hately
-----Original Message-----
Sent: 16 May 2002 17:14
To: Multiple recipients of list ORACLE-L
The "compress=y" option doesn't have any effect on how data is stored in the
export dump file, only some of the metadata.
It directs the EXP program to recalculate the DDL for all of the tables and
indexes (instead of just using the settings in the data dictionary) so that
all space previously allocated for the object is now contained in a single
extent. In other words, if a table being exported had a STORAGE clause
like:
storage (initial 1M next 1M pctincrease 0)
and it currently had 500 extents allocated to it, then the EXP program would
store the DDL for the table in the export dump file with a new STORAGE
clause:
storage (initial 500M next 1M pctincrease 0)
There are several flaws with this mechanism:
* the table may be completely empty of rows, but 500M will still be
allocated for its initial extent. The COMPRESS=Y option doesn't consider
the possibility that rows may have been deleted...
* the idea that a single extent is better than many extents is complete
nonsense (I wrote a paper in spring 2001 on this, posted at
www.EvDBT.com/library.htm, entitled "Myths About Extents And
Performance")...
* the idea that a single large extent is better than many extents
actually increases the probability and problems associated with "tablespace
free-space fragmentation" instead of reducing it. Think about it:
everything may look "good" immediately after import, but what happens after
a few weeks or months?
Although COMPRESS=Y is the default, I strongly advise that you use
COMPRESS=N to disable this functionality, in most cases. Just my $0.02...
----- Original Message -----
To: "Multiple recipients of list ORACLE-L" <[EMAIL PROTECTED]>
Sent: Thursday, May 16, 2002 9:33 AM
Patrice - That would be correct. If you run export interactively, the prompt
that is provided is "compress extents (y/n)".
Dennis Williams
DBA
Lifetouch, Inc.
[EMAIL PROTECTED]
-----Original Message-----
Sent: Thursday, May 16, 2002 10:08 AM
To: Multiple recipients of list ORACLE-L
I don't know whether this is a tangent, but I notice that on the windows
platform, "compressed" exports can still get 85% compression when zipping
them with WinZip.
Obviously Oracle "compressed=y" doesn't mean "compress the export file", it
just means that it places all the segments contiguously in the export file.
Right?
Regards,
Patrice Boivin
Systems Analyst (Oracle Certified DBA)
Systems Admin & Operations | Admin. et Exploit. des systèmes
Technology Services | Services technologiques
Informatics Branch | Direction de l'informatique
Maritimes Region, DFO | Région des Maritimes, MPO
E-Mail: [EMAIL PROTECTED]
--
Please see the official ORACLE-L FAQ: http://www.orafaq.com
--
Author: Boivin, Patrice J
INET: [EMAIL PROTECTED]
Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
San Diego, California -- Public Internet access / Mailing Lists
--------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in
the message BODY, include a line containing: UNSUB ORACLE-L
(or the name of mailing list you want to be removed from). You may
also send the HELP command for other information (like subscribing).
--
Please see the official ORACLE-L FAQ: http://www.orafaq.com
--
Author: DENNIS WILLIAMS
INET: [EMAIL PROTECTED]
Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
San Diego, California -- Public Internet access / Mailing Lists
--------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in
the message BODY, include a line containing: UNSUB ORACLE-L
(or the name of mailing list you want to be removed from). You may
also send the HELP command for other information (like subscribing).
--
Please see the official ORACLE-L FAQ: http://www.orafaq.com
--
Author: Tim Gorman
INET: [EMAIL PROTECTED]
Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
San Diego, California -- Public Internet access / Mailing Lists
--------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in
the message BODY, include a line containing: UNSUB ORACLE-L
(or the name of mailing list you want to be removed from). You may
also send the HELP command for other information (like subscribing).
____________________________________________________________________________
________________________
This email and any attached to it are confidential and intended only for the
individual or
entity to which it is addressed. If you are not the intended recipient,
please let us know
by telephoning or emailing the sender. You should also delete the email and
any attachment
from your systems and should not copy the email or any attachment or
disclose their content
to any other person or entity. The views expressed here are not necessarily
those of
Churchill Insurance Group plc or its affiliates or subsidiaries. Thank you.
Churchill Insurance Group plc. Company Registration Number - 2280426.
England.
Registered Office: Churchill Court, Westmoreland Road, Bromley, Kent BR1
1DP.
--
Please see the official ORACLE-L FAQ: http://www.orafaq.com
--
Author: Hately Mike
INET: [EMAIL PROTECTED]
Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
San Diego, California -- Public Internet access / Mailing Lists
--------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in
the message BODY, include a line containing: UNSUB ORACLE-L
(or the name of mailing list you want to be removed from). You may
also send the HELP command for other information (like subscribing).
--
Please see the official ORACLE-L FAQ: http://www.orafaq.com
--
Author: Tim Gorman
INET: [EMAIL PROTECTED]
Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
San Diego, California -- Public Internet access / Mailing Lists
--------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in
the message BODY, include a line containing: UNSUB ORACLE-L
(or the name of mailing list you want to be removed from). You may
also send the HELP command for other information (like subscribing).
