Re: Few very BASIC Q's - pls not let to die :)
Date: 1995/05/12
Message-ID: <Pine.SUN.3.91.950512084337.5818C-100000_at_seatimes>#1/1
On 7 May 1995, Rashid Karimov. wrote:
> Is it possible to have more that 1 database opened in the
> same time on the same computer ( I use ORACLE 7.0.16
> under SOLARIS 2.4) ? How ?
Yes. Each database would have it's own instance, set of processes running, and it's own ORACLE_SID value. As long as you have enough main memory, cpu horsepower, and IO bandwidth, there is nothing to prevent multiple databases from running on the same machine. Be aware though, that the total number of users for all databases must conform to the license level you purchased for that box. That is, if you have a 30 user license and three databases of equal usage, then you need to ensure that each database has no more than 10 users (or that the total doesn't exceed 30 for all three).
> Can one( the same ) instance serve multiple databases ? Or you have
> to start an instance for every database you want to
> open ?
No and Yes. Perhaps you are confusing schema (of which multiple can be in a single database) with database? Each database has it's own instance.
> The SGA area - does it serve all mounted/opened databases or
> there is a SGA per database ?
Each instance has its own SGA. There is one per database that is started.
> What's init****.ora file ? You have to create/customize
> one for every new database ?
A bunch of parameters to configure how this particular database will run. You need a custom one for each database. That's why the ORACLE_SID is part of the name. See the Adminstrators Reference Guide for a list of the parameters.
> The database which is created during the installation -
> does it have any special meaning ? In other words ,
> shoud you _always open/mount it for ORACLE to work ?
Nope. I don't let the installer build mine. I want a whole lot more control over what is happening.
> Is it mounted automatically ?
Depends on how oratab is set up.
> Help/error messages for different ORACLE binaries -
> are they stored in that database ? Or binaries are
> able to access some files with that stuff w/o actually
> working with ORACLE ?
The error messages and numbers are not dependent on having this 'special' database. There is nothing special about it at all.
> The oratab file - what's its purpose ? Can one add
> the entries to that file to get new databases be
> opened/mounted automatically ?
It is used by dbstart and dbshut to determine what databases to automatically start and shut when the system is started or shut. The third flag should be a 'Y' for things to happen automatically. You also need to have the host startup and shutdown scripts call the dbstart and dbshut (see the installation guide for more details).
> When one creates new database/s - does it modifies
> some ORACLE ( system ) tables ?
> In other words - to remove a database - is it enough
> just to remove all associated physical files ? After
> which ORACLE forgets about that database completely ?
Just removing all the database files is sufficient. There are no special tables hidden anywhere that keep track of this stuff. That's part of the reason for the init$SID.ora parameter file.
> I'm sorry for these Q's - for some guru they should seem
> really stupid - but I need the answers to get peace in
> my mind :))
Perhaps. But then we all started someplace and grew in knowledge by using the system. The most stupidest question is the one that isn't asked!!
Feel free to ask further if the above answers don't make sense to you (or to the other folks who didn't want to ask but needed to know).
--Steve
+----------------------------------------------------+ | Steve Butler Voice: 206-464-2998 | | The Seattle Times Fax: 206-382-8898 | | PO Box 70 Internet: sbut-is_at_seatimes.com | | Seattle, WA 98111 Packet: KG7JE_at_N6EQZ.WA | +----------------------------------------------------+All standard and non-standard disclaimers apply. All other sources are annonymous. Received on Fri May 12 1995 - 00:00:00 CEST