Re: High Availability

[oliver.wenzel@xxxxxxxxxxxxxxxxxxxxxxx]

Hi,

>We are considering replicating some of our production boxes and have just
>started looking at what is available.  The OMS/ODS, DataMirror and Mimix
>seem to have the highest profile but I have also seen offerings like 
*noMAX
>and Echo2.

Well, we are still in the implementation phase for DataMirror. Production 
machine is an 820 and
backup a new 810.

Mirroring itself is quite easy to setup and maintain, but there are a 
couple of gotchas, especially
for really switching to the hot-standby machine. And for the switching 
process, you don't get too much
support from the vendor.

- Make sure to get license keys for the backup machine for all your 
products
- Mirroring spoolfiles doesn't work too well (all mirrored spools are in 
rdy state) - we switched it off
- If you use the job scheduler, there are additional problems
- Replicating source files can be a problem
- Journalling all our files created a heavy performance problem. We had to 
exclude our EDI application to 
  get decent performance.
- Make sure you have a really fast connection between your systems. 
Especially when the connection breaks 
  for some time, a lot of replication entries will queue up (and you'll 
have to keep the journal receivers
  online). A one-day downtime of the backup system (or connection) might 
well force you to do a complete data
  reload on the backup.
- Plan your application restart procedures. 

Some of these points might only apply to DataMirror - I dunno if other 
products would be better in handling
spoolfiles or some other stuff.

Regards,

Oliver