Re: Oracle vs Informix comparison

While both methods will work, there are distinct advantages of using log based/async replication over triggers. If we are using trigger based replication and are in a transaction, then the transaction must suffer the time-lag of the replication being processed on the remote machine. In the best of cases where the trigger is simply copying the data into another table within the same instance, there is still additional overhead. Also, if this approach requires that a lot of triggers/stored procedures be created which opens the possibility of application level mess-ups. CDR (or as it is now called Enterprise Replication) works off the log files that are used for rollback and recovery. That means that there is no increase in the code path of the transaction that is being replicated. We simply have a seperate thread in the engine that is scanning the tail of the log file and copying data which is to be replicated to a send queue. This allows a single thread to manage the replication, rather than all of the triggers/stored procedures that would be necessary in a trigger based replication scheme. This results in much less overhead, less requirements in the procedure cache pool and fewer possibilities of failure. Madison Pruet