Sharing an Instance vs Using Separate Instances??

I'm curious if having apps share an instance (separate schemas) is a common practice? We do some of it here (we have some small OLTP apps sharing instances, DSS apps sharing others) but there are issues; different software packages may be ok under the same version of the dbms when you start but eventually separate instances may be required for app/dbms compliance (i.e. you may want to upgrade the dbms and that may be ok for certain apps but not for others), availability (downtime for one could mean downtime for all), contention, etc.

On the other hand, for small apps, a separate instance per app may be overkill in terms of resources. And you end up having to administer a larger quantity of instances; 20 small instances vs 5 larger, shared instances for example (i.e. viewing 20 alert logs vs 5, etc). And multiple instances per UNIX machine will consume available memory more quickly (ever have to balance the "processes" init parameter between multiple instances on a machine?)

Any feedback is appreciated. Thanks.
-Rick P Received on Mon Oct 09 2000 - 11:39:46 CDT