But the last time I looked at it, you had to enable supplemental logging at the database level if you wanted to use logical standby. Two side effects -
1) As you said, you need a unique/primary key, and database supplemental logging copies such a key into the redo for every change to a row: but if there is not uk/pk, then the whole row is copied. 2) The copy into redo is engineered by copying into the UNDO first - and since changes to GTTs are recorded into the UNDO, this means you get an extra volume of UNDO, hence REDO on all changes to 'supposed to be low-cost' GTTs. The other feature of logical standby is that Oracle scrapes the redo log to generate LCRs (logical change records) which are then checked against your 'Streams rule-sets' - and then written into the local database for propagation to the remote via AQ mechanisms. The overheads could be quite significant. 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 One-day tutorials: http://www.jlcomp.demon.co.uk/tutorial.html Three-day seminar: see http://www.jlcomp.demon.co.uk/seminar.html ____UK___November 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" <[EMAIL PROTECTED]> Sent: Tuesday, December 09, 2003 9:59 PM Hi Vi, Rows NEED unique identification. So, if there are bunches of raw data with no unique identifier whatsoever (remember, rowid is not allowed) LSB can't generate a where-clause what row to update or delete on the SB database. It's generating SQL based on redolog info, and has to come up with an UPDATE <table> SET .... WHERE <unique id> = <unique id>. The unique id may be a multi-column key. There is an escape. Enabling supplemental logging can add extra info to do the unique identification, when no usable keys are available. This will cause some extra logging to be generated, there ain't no such thing as a free lunch. For detailed information read chapter 4.1.5 & 4.1.6 in the Oracle Data Guard Concepts and Administration manual, part no. A96653-02. regards, Carel-Jan At 15:54 8-12-03 -0800, you wrote: -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Jonathan Lewis INET: [EMAIL PROTECTED] 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: [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).
