Re: 30 instances on one host

Sean M wrote:

> Daniel Morgan wrote:
> >
> > Sean M wrote:
> >
> > > I could be misinterpreting Daniel, but I think he's still talking about
> > > a 1-to-1 relationship between instance and database, but that he's only
> > > running a subset of his databases at one time. So the host has, say, 6
> > > databases on it, but only 3 of which are actualy instantiated at any
> > > given point (the others are just shutdown, not consuming any resources
> > > other than disk space).
> > >
> > > Regards,
> > > Sean M
> >
> > I've never talked about a 1:1 relationship between databases and instances. The
> > CREATE DATABASE command has a parameter for MAX INSTANCES.
> >
> > I just wasn't sure that, while trying to follow the thread and learn from the
> > rest of you, that you were all talking about the same thing. Some seemed to use
> > the word instance in the technically correct manner while others were using it
> > to mean instance. And no one seemed to notice or care except this poor soul who
> > was hanging onto every keystroke.
> >
> > I've had lots of servers with multiple databases. But multiple instances on one
> > machine? A few times but I've never felt good about it.
> >
> > Daniel Morgan
>
> OK, that's the last time I try to interpret what someone else meant and
> speak for them. :) So, please, Daniel, what are you talking about?
> You've now lost me. Strictly speaking, an Oracle instance (as Pete
> already said) is the sum of SGA and background processes. An Oracle
> database consists of controlfiles, datafiles, and online redo logs. The
> true relationship is many instances to one database. But that's only
> possible if RAC/OPS is involved. Otherwise the relationship is
> one-to-one, and since relatively few sites run RAC/OPS, the words tend
> to get used interchangably. I assumed all of us here in this thread
> understand these definitions and were on the same page, but now I'm not
> sure... So Daniel, can you please explain what you mean by having
> multiple databases on one machine but not multiple instances (which
> implies a many databases to one instance relationship)?
>
> Thanks,
> Sean M

I don't want to belabor the point. And on reading my previous posting I realize I was typing a bit faster than I was thinking. I'll try again and this time proof read what I've written.

I think at some level we all know that a database does not equal an instance. That they are two entirely different things. I was posting to the thread because it appeared to me that a conversation was taking place between those people using the word instance in its true technical meaning and others using it to mean database. I was just trying to obtain a clarification. To be sure that when someone said "30 instances" whether they meant 30 system tablespaces, 30 temp tablespaces, 30 sets of

log files and control files ... or whether they mean that they had Oracle installed
on the box 30 separate times ... or whether they meant that they had 30 copies of
each Oracle process in memory.

It was just a request for a clarification ... nothing more. Sorry if I was unclear.

Daniel Morgan Received on Fri Jun 21 2002 - 10:26:56 CDT