Re: Oracle vs Informix comparison

David Williams <djw@smooth1.demon.co.uk> wrote: >In article <58if4p$oca@dfw-ixnews2.ix.netcom.com>, Rajashekar >Sundaramurthy <rajsekar@ix.netcom.com> writes >>You wrote: >> >> You are describing a synchronous replication scenario wherein the >>updating transaction waits for the replication to be completed before >>the commit occurs. >> >>In Oracle7 (which uses triggers/stored procedures and deferred >>transaction queues) to handle replication, the simpler update-anywhere >>environment works as follows ( for asynchronous replication) >> >>Application inserts a row into a table at the master site; >>The AfterInsert trigger fires which updates a snapshot log with the >>ROWID of the newly inserted row; >>Application commits the insert transaction; >> > > There is still a performance problem - I write all the data necessary > to redo the update to a transaction log. Why should I also write it to > a snapshot log?? It is a waste of time. That is an easy question to answer... Although the entry has been written to the transaction log - the snapshot log is required to sync. the data at the distributed sites. It would be a nightmare of a job to go through transaction logs checking to see if the data required to update a snapshot was listed. The whole concept of the snapshot is really a timing issue, the update does not necessarily get written out to the distributed site at the time the transaction is committed. It is up to the DBA or system designer to decide when data is replicated. > Also why rewrite the code to > performance the transaction on the site you replicate to. The code for > transaction follforward is already written/debugged/tested in a > production environment. Why a) Have more code which is not as > efficient and clear will not be as stable b) Write the transaction > 1.1 times to disk instead of once.? > >-- >David Williams _/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/ Gordon E. Hooker MACS PCP 25 Clarke Street Ripley Queensland Australia Phone 61-7-32940555 Email gordonh@thehub.com.au _/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/ We are just two lost souls living in a fish bowl Year after year Pink Floyd