replication performance: Informix vs Oracle?

[abc_18]

We had performance problem when replicating a lot of changes with Informix 7.x. Environment: HP-UX 11.11, two machines, on in US the other in Europe.

Q#1: has Informix replication performance improved noticably between IDS 7.3 and IDS 9.3?

Q#2: if we migrate to Oracle (say, 9i), should we expect better performance?

Q#3: are there any benchmarks for db replication performance?

Apologies in advance for the sketchy details; I'm asking this for a friend.

[Steven E. Protter]

Q#2 If you tuned it correctly you should expect better performance of Oracle 9i versus other versions. The memory use is higher and if your box is short of memory, the upgrade will result in slower performance.

Q#3 There are testing tools available to guage database performance. They are expensive and not as accurate as say a group of 10 users going out of their way to pound a database.

Q#1 I would look at how the disk is set up if you are having performance problems. Oracle will peform quite poorly if redo logs, data or index is on raid 5 disk. Any files needing good write performance should be on raid 1 or raid 10 storage. The higher the raid parity, the slower the writes and bigger the bottlenecks.

SEP

[Steve Lewis]

If you go from 32 bit to 64 bit you can expect the replication performance to suffer considerably (twice as many bytes to send). Later versions of informix have much bigger logical log records so it won't get any quicker in 9.xx although it may be more reliable.

I would recommend you go to 9.40.FC5 or even 10.x if you want to upgrade informix.
If you are using step-wise commits (ie synchronous replication) then you can expect it to crawl - definitely go for asynchronous replication for continental configurations.

Cannot say for the speed of Oracle replication because I haven't implemented it, but I did the DBA course and presume that it works in a similar manner to informix.

One other thing - a lot depends on your line quality and the route taken between hosts - performance can vary considerably from day to day.

One benchmark that I did find was that on a pair of L class (2x360Mhz) servers, when informix was worked as hard as possible, the replication required a 2 megabit line to keep up with the the databases. It would wake up every 30 seconds and blast a load of replication information to the other end.