Re: How much instances per server?

Proper init.ora parameters and configuration you can eliminate rollback contention. Done it on sites with 3,000 users not very difficult.

You are going to have something similar to redo contention with multiple instances since you have to put the redo somewhere. The disk IO will be flooded no matter which scheme you use. Of course, if you put enough disks together in either case you can reduce contention.

Not sure what independent backup and restore has to do with anything. If the instances or schemas are seperate then I don't see how that is applicable. Certainly if you want another instance as a backup I see no problem with that. Multiple instances is not a bad thing unless you do too much of it.

Actually, you can have priviledges apply on a per schema mode. Sure someone is "root" somewhere, but that is true in multpile instances you just have a "root" for each instance. The users and privledges should not be given dba privledges anyway.

Not sure what you mean by commercial packages using prescriptive schemas.

Having done a lot of performance testing in the NT environment and HPUX having a lot of instances (in NT over 5) and a busy system you are better off with schemas than instances in the majority of cases. Jim

"Fuzzy" <granta_at_nospam.student.canberra.edu.au> wrote in message news:3b0b16b2.9954183_at_newshost.interact.net.au...
> On Tue, 22 May 2001 12:41:06 GMT, "Jim Kennedy"
> <kennedy-family_at_home.com> wrote:
>
> >Why not make it easier and just have multiple schemas? (Performance is
> >never secondary; everyone says it is then bitches when it bites.) The
 user
> >will have the same effect and with less maintenance and better
 performance
> >than multiple instances. Theoretically, you can have a very large
 number;
> >in practice after about 5 performance really starts to tail off.
>
> Why not use multiple schemas? Let's see
>
> - Rollback contention
> - Redo contention
> - No independent full backup
> - No independent restore
> - DB-wide privileges apply to all schemas ... not just the one you're
> using to mimic a database.
> - Problems with commercial packages that use prescriptive schemas
> - Every other major db (DB2, Informix, Sybase, SQL Server 2k) supports
> multiple DBs per instance, AND schemas within each DB.
>
> Oracle is really good at a great many things ... but they're 10 years
> behind on this particular topic.
>
> Ciao
> Fuzzy
> :-)
>
Received on Tue May 22 2001 - 21:57:27 CDT