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Hi,
Iam new to Oracle and would appreciate any clarifications on
these doubts I have:

1. Iam reading the documentation and it says that Oracle DB Server is
basically Oracle Database and Oracle instance. What I understand is
there is one Oracle DB and there can be 1 or more Oracle instances. So
my question is, when can there be more than one Oracle instances?

2. Is there always a one-to-one relationship between a schema name and
the username?

3. Can the actual data corresponding to a Schema be in one datafile or
it can be shared in more than one datafiles and also can a datafile
contain the information pertaining to more than one schemas?

Thanks!

"leostar10" <leostar10@gmail.com> wrote:

>Hi,
> Iam new to Oracle and would appreciate any clarifications on
>these doubts I have:
>
>1. Iam reading the documentation and it says that Oracle DB Server is
>basically Oracle Database and Oracle instance. What I understand is
>there is one Oracle DB and there can be 1 or more Oracle instances. So
>my question is, when can there be more than one Oracle instances?
>
>2. Is there always a one-to-one relationship between a schema name and
>the username?
>
>3. Can the actual data corresponding to a Schema be in one datafile or
>it can be shared in more than one datafiles and also can a datafile
>contain the information pertaining to more than one schemas?
>
>Thanks!

Time to read more ( especially the Concepts manuals)...

1: search this group ( Google's advanced Group search is good for this) for DA Morgan's excellent definitions/distinctions
of these

2: All schemas are based on 1 and only 1 user name each..Not all users have schema objects, however.

3: Datafiles are not involved directly, Oracle places data in Tablespaces specified by the creator of the table..These
tablespaces may ( and often do) span multiple datafiles. Your concept of 'sharing' may be off..Any Schema owner ( the user
that created it) may grant access to data in that schema to any other user...Does not matter where the data is physically
stored.

If you are coming from another Database skill set, ( especially SqlServer) , you will be better off if you 'forget' most of
the terminology/methodology you know from there - It will confuse things, especially since sqlServer uses the same terms for
things and concepts that are completely different in Oracle.





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leostar10 wrote:
> Hi,
> Iam new to Oracle and would appreciate any clarifications on
> these doubts I have:
>
> 1. Iam reading the documentation and it says that Oracle DB Server is
> basically Oracle Database and Oracle instance. What I understand is
> there is one Oracle DB and there can be 1 or more Oracle instances. So
> my question is, when can there be more than one Oracle instances?
>

RAC


> 2. Is there always a one-to-one relationship between a schema name and
> the username?

Yes
>
> 3. Can the actual data corresponding to a Schema be in one datafile or
> it can be shared in more than one datafiles and also can a datafile
> contain the information pertaining to more than one schemas?

You set the user/schema to have a default tablspace that can have more
that one datafile. Multiple users can use the same tablespace, so yes.

>
> Thanks!

Thanks for the information guys. I did try to look for DA Morgan's
listing, but got more than 3000 responses ..anycase, I will try to
understand about the case where we can have more than oracle instances
on a single Database..

Hi,

I'll be starting an Oracle 10g study group next month. It will be free
and you and anyone else who is interested is welcome to join. Some
preliminary information can be found at:
http://oracle10gcertification.com

Best Regards,
BP

leostar10 wrote:
> Thanks for the information guys. I did try to look for DA Morgan's
> listing, but got more than 3000 responses ..anycase, I will try to
> understand about the case where we can have more than oracle instances
> on a single Database..

Right here.
--
Daniel A. Morgan
http://www.psoug.org
damorgan@x.washington.edu
(replace x with u to respond)

Hi Daniel,
That must be there 3001st post ..can you point me
to the message you had posted which explains Database/Instance scenario
in detail. If not, can you explain in a few words a possible scenario
of multiple Oracle instances sharing the same DB.

Thanks.

leostar10 wrote:
> Hi Daniel,
> That must be there 3001st post ..can you point me
> to the message you had posted which explains Database/Instance scenario
> in detail. If not, can you explain in a few words a possible scenario
> of multiple Oracle instances sharing the same DB.
>
> Thanks.

Multiple instances connecting to one database = RAC (Real Application
Clusters)

There is a huge amount on them all over the web and especially at
http://tahiti.oracle.com.

HTH
--
Daniel A. Morgan
http://www.psoug.org
damorgan@x.washington.edu
(replace x with u to respond)

Thanks!