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

        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 ? 

	Can one( the same ) instance serve multiple databases ? Or you have
	to start an instance for every database you want to 
	open ? 
	The SGA area - does it serve all mounted/opened databases or
	there is a SGA per database ? 

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


	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 ? 
	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 ?


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


	4.
	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 ? 


	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

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