There is a problem with this approach that may only become apparent at high concurrency.
Since you are operating with two-phase commits, you may come up against the case where "writers block readers". Your client issues a commit to both servers. Each server get the PREPARE message, and when both have responded, each gets the COMMIT message. Between the PREPARE and COMMIT, any blocks updated in the transaction cease to be available to ANY query that started after the PREPARE arrived. For the (hopefully) brief interval between the prepare and commit, neither database knows whether the transaction as a whole has prepared or committed, so any process that wants to see the current version of the data has to wait until there is a known current version. In a high-concurrency system, a problem that used to be "buffer busy waits" on updates only can turn into enqueue waits on updates and queries. 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: Saturday, December 13, 2003 8:19 PM Yep, I also think so. I'm currently developing a small prototype for this kind of transparent proxy, which I'll post here when it's stable... Tanel. > Tanel, > > I think this is a good solution, provided the application can handle > two phased commit protocol across both the databases, else there > could be orphan records on one or both these databases. > -- 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).
