Re: Basic Oracle Concepts

"Mark C. Stock" <mcstockX_at_Xenquery .com> wrote:

>
><sybrandb_at_yahoo.com> wrote in message
>news:1122551255.818339.55450_at_g44g2000cwa.googlegroups.com...
>> No, one instance manages one database. Period.
>> You have
>> instance
>> |
>> |
>> database
>> |
>> ---------------------------------------
>> | |
>> scott schema hr schema
>>
>> That is 2 schemata in 1 database.
>>
>>
>> Users are connected to a *database*, NOT to a *schema*, and they can
>> access whatever schema, they have been allowed to access.
>> --
>> Sybrand Bakker
>> Senior Oracle DBA
>>
>
>depending on your DBMS background, 'connect to a database not a schema'
>might give the wrong impression. here's a bit more detail..
>
>users connect to a single schema in a single database -- ie, on connection
>they supply a schema/user name, password, and database service name (the
>schema/user credentials may be defaulted or be tied to the OS or network,
>and the database service name may also default)
>
>once connected, all access privileges are in the context of that original
>connection schema -- which likely includes access that has been granted to
>objects owned by other schemas, whether that access has been granted
>explicitly to the connect schema (grant select on emp to calvin) or via a
>role that the connect schema has had granted to it (including the PUBLIC
>role)
>
>all object references are assumed to be objects owned by the connection
>schema, unless a private or public synonym exists that encapsulates the
>objects owner (and perhaps a path to another database, ie, a database link)
>
>additionally, the ALTER SESSION SET CURENT_SCHEMA statement sets any other
>schema as the default context for unqualified object references -- but it
>does not change the session's privileges (privileges assigned to the
>connection schema remain in affect)
>
>there is also a confusing 'BECOME USER' system privilege, but this appears
>to only be used by Oracle utilities (such as EXP) and programs that access
>Oracle via the OCI (Oracle Call Interface)
>
>++ mcs
>

The language does get circular and confusing sometimes..You connect to an instance ( called a database, sometimes, incorrectly. In Oracle, as has been posted by DA Morgan,a database is physical files, datafiles, undo files, tempfiles residing on a hard disk along with their associated control files and log files.)

The schemas are collections of objects 'owned' by USERs ( including SYS and SYSTEM ) and those users can grant other users rights to access, modify, remove or otherwise treat those objects as their own .

You connect to an instance as a USER ( not a schema, a schema is not a person ) ...

----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- Received on Thu Jul 28 2005 - 08:46:28 CDT