Re: Sharing an Instance vs Using Separate Instances??

papaj_at_acsu.buffalo.edu (Richard A Papaj) wrote in <8rssd6$875$1_at_prometheus.acsu.buffalo.edu>:

>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

Rick,

FWIW, here's mine: I tend towards fewer instances rather than more. Machine resources, as you point out are an issue. So is database managment. Oracle provides the notion of separate schemas, so I figure "why not use them?". If, instead, you have two instances running, your odds of having an instance down are twice as high. Perhaps it will only cause half the damage, but whoever cleans up the problems will be doing twice a much of it.

The decision really has to come from you, by considering how much management you & yours are prepared to do, how much "machine" you have available, and the criticality of the apps involved. If you're concerned about outages, perhaps you should have a Parallel Server configuration on two machines.

It's my opinion that fewer instances results in less managment - or better managment of the single instance rather than sub-par management of multiple instances.

Managing package / application versions is certainly an issue too. If it becomes a critical problem, split into two instances in the future. If I was my call, I'd resist the split kicking & screaming till the bitter, stinkin end - but I'm a little stubborn.

ws

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