I have DB2 v9.1 ESE running on Windows (one system is 32 bits and all other 8 are 64 bits).
In some of those physical servers (QA, Development) I have multiple DB2 instances running under the same OS.

I am aware of 32bits memory limitation but regarding those 64bits servers I would like to know if having more than one instance would be better than multiple instances inside the same server. Of course considering those obvious cases when one database is basically DSS type and the other one is OLAP that I know would make more sense creating 2 separate instances.

It might sound kind confusing what I wrote above, but not considering DSSxOLAP types of databases, what kind of benefits I could get having multiple instances in the same server?

Thx

Is there any purpose behind having multiple instances?

There are couple reasons such as making them independent so that I can bounce DB2 instance for whatever reason without impacting other users in different databases, but my question is if does make any good or bad having multiple instances.

Thx

True, you gave the answer yourself...

It is always good to have different instances for different requirements(like QA, development)

For eg: if you need a high performance configuration/needs more resources for a particular application, you can tune it accordingly if you have seperate instance. If you have only one instance for all applications, you cannot do that.

You can restrict users to access only authorized data (like payroll) by keeping it in a seperate instance. If you have it in a single instance, then the database owner will have a permission to access data.

There could be some other advantages also....

Thanks,
Madhavi