Re: Few very BASIC Q's - pls not let to die :)

In article <3oip1j$mpr_at_ankh.iia.org> rashid_at_haven.ios.com (Rashid Karimov.) writes:
>From: rashid_at_haven.ios.com (Rashid Karimov.)
>Subject: Few very BASIC Q's - pls not let to die :)
>Date: 7 May 1995 15:29:54 GMT

> Hi there folx.

> I have a few Q's about - very basic ones , I think ,
> but I wasn't able to find answers myself ( I do have
> some expirience with different RDBMS ) , albeit I
> tried real hard ( all books on ORACLE we have here
> in NYC were tried ) .
 

> OK.

> 1.
> As I got , one can have more than 1 database , which is
> a _physical stuff and carries tablespaces ( SYSTEM is
> the only one which is created automatically ),tables
> themselves and redo/control files.
 

> 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, just create a new database, for instance by using the installer. You can have as many databases open as your memory, semaphores, processes, etc allow.

> Can one( the same ) instance serve multiple databases ? Or you have
> to start an instance for every database you want to
> open ?

When you have the parallel server option you can have multiple instances access the same database. One instance cannot access more than one database (not counting distributed databases). Instances : databases = n : 1 It's only relevant with loosely coupled processors like vax clusters.

> The SGA area - does it serve all mounted/opened databases or
> there is a SGA per database ?

Each instance has it's own SGA. A SGA is coupled with an instance, not a database.

> What's init****.ora file ? You have to create/customize
> one for every new database ?

An init<SID>.ora file contains the initialisation parameters for an instance. Things like the number of buffers, processes etc go in there. When you use the installer to create an instance/database, one is created for you in the O_H/dbs directory.

> 2.
> 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 ?
> Is it mounted automatically ?

It's just a database like every other. You can use it or loose it. It's opened automatically when you create it. To have it opened at system startup, you need to make changes to your rc2.d directory and your oratab file.

> 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 ?

Messages are stored in *.msg and *.msb files. msg's are readable, while msb's are used by program's. Each program has it's own *.msb and *.msg files located in various directories.

> 3.
> The oratab file - what's its purpose ? Can one add
> the entries to that file to get new databases be
> opened/mounted automatically ?

If you want your database to open/close automatically on system startup/shutdown you have to put a line in your oratab, displaying the following : oracle_sid:oracle_home:Y

> 4.
> When one creates new database/s - does it modifies
> some ORACLE ( system ) tables ?

It only modifies files belonging to that particular database. Common files, like oratab, you have to maintain yourself.

> 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 ?

Yes, except for the files you modified yourself, e.g. oratab.

> 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 :))
 

> Personal E-mail would be appreciated
 

>Rashid
>--
> ------------------
 

> Beyond the horizon of the place we lived when we were young
> In the world of magnets and miracles
> Our thoughts strayed constantly and without boundary
> The ringing of the division bell had begun ...
> -=PF, The Division Bell=-

Greetings,
Frank Received on Sun May 07 1995 - 00:00:00 CEST