Re: fast commit

Note in-line

Regards

Jonathan Lewis
http://www.jlcomp.demon.co.uk

  The educated person is not the person
  who can answer the questions, but the
  person who can question the answers -- T. Schick Jr

Next public appearance2:
 March 2004 Hotsos Symposium - Keynote
 March 2004 Charlotte NC - OUG Tutorial
 April 2004 Iceland

One-day tutorials:
http://www.jlcomp.demon.co.uk/tutorial.html

Three-day seminar:
see http://www.jlcomp.demon.co.uk/seminar.html ____UK___February

The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html

• Original Message ----- To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: Thursday, January 22, 2004 6:29 AM

Hi list,

1)Why fast commit generate no redo ?

It's called a fast commit BECAUSE it doesn't generate redo
(except for a tiny bit that describes the change to the transaction
table entry in the segment header block that marked the transaction as active).

It doesn't need to generate redo because it's going to leave
(most of) the lock and change information on the blocks that
have been changed, and let some other visiter to the blocks clean up the mess.

2)Is delayed cleanout generate redo?

Delayed "block cleanout" - where a later operation simply READS a messy block and cleans it up (by referring back to the transaction table to get the necessary commit details) will generate redo.

Delayed-logging "block cleanout" - which occurs when the first transactions cleans out a few of the blocks it has dirtied but does not log the cleanout - is effectively not going to generate redo, as the next transaction to MODIFY the date will generate some undo which looks as if it started from a clean block, rather than the partly dirty block that is really there - so the cleanout is effectively free.

3)In a block dump even after transactions commit why it shows lock 1 in ITL?

Because Oracle doesn't clean the block out properly, it will either not revisit it at all (1), or just revisit the ITL and a couple of header bytes (2).

Thanks in advance.
Syed

-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: Jonathan Lewis
  INET: jonathan_at_jlcomp.demon.co.uk

Fat City Network Services    -- 858-538-5051 http://www.fatcity.com
San Diego, California        -- Mailing list and web hosting services
---------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
to: ListGuru_at_fatcity.com (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).