Re: Oracle question from a Sys. admin, re: Solaris performance

tonij67_at_hotmail.com wrote:
> Yes, they are creating separate instance for each "client". The way
it
> works is there is an in house product that has been developed and
this
> product is sold to external clients, which then connect to our
systems
> to use it. Each instance has its own mount point for datafiles,
> exports and redos. I can see a separate pmon and smon for each
> "client" so with that information is it safe to assume each client
has
> their own instance? (my lack of DBA knowledge should be evident by
now)

Yes, ps -aux|grep dbw ought to tell how many and the names of each instance (IIRC the solaris ps).

Seeing as you have a big V box, this may not be so bad. One of the main reasons for having multiple instances is to be able to have different restoration requirements - if client 23 blows up his data, it may be easier to restore just that client. The more normal way to do this in fewer instances would be to have clients assigned to tablespaces, and back up those separately. You better not be depending on exports to be backups. A lot depends on your service agreements.

Another reason would be performance - if client 37 decides to start doing stupid cartesian joins, just that one instance would be seriously affected (well, depending on cpu's...). The more normal way to handle this would be to set up resource limits.

Probably the most difficult reason to argue against would be differing upgrade requirements. If any number of your clients may want to stick with a current version of Oracle (and this may apply even more to your app version, assuming you have version control) and any number may want to upgrade, that would be a strong reason to have separate instances. Weighting the importance of this is a management decision, and it can be bad for customer relations to make them do, or not do, upgrades. There have been many posts in this group about customers being stuck on unsupported versions because their vendor wouldn't upgrade. Not to mention the screams when Oracle requires an O/S upgrade with an Oracle upgrade (don't think they'll make that mistake again).

As a simple-minded way of doing things, one instance per customer and throw out a huge amount of expensive hardware is workable, until things screw up. But it really is not the best way to do things, you need an experienced, capable DBA to set things up properly. And you definitely need someone who understands Oracle, the application, and how to react when things go wrong. Only experience with Oracle can help with the latter.

jg

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