2 INSTANCES IN ONE M/C?

[Wolf]

Sreddy, you write

instance/database------> Normal configuration
instances/database----> OPS(Oracle Parrallel Server

Could you clarify? I'm still new to Oracle and the distinction between intance and database is still not very clear for me. :-(

I know it's probably a newbie question, but I have to start somewhere no? :-)

Thanks!!

[sreddy]

I prefer to rephrase

instance per database------> Normal configuration
instances per database----> OPS(Oracle Parrallel Server

sorry about the confusion.

Look at :

Instance as only back ground processes PMON, SMON,DBWR,LGWR etc., and SGA.

Database as datafiles,tablespaces,tables etc which has data in it.

[Edited by sreddy on 01-23-2001 at 04:50 PM]

[sonaliak]

Thanks for clarification sreddy! Yes, I am little bit confused with the instance !
I know this is a basic question, but what is the instance then ??
I thought that SID in tnsnames.ora is the instance ID which should be unique.
So I was thinking that each service is a instance and that the database can have multiple instances/services on the same server. Is their any limit on how many services you can have for a database ?

[sreddy]

SID (System Identifier) is an instance(SGA+background processes like PMON,SMON.DBWR,LGWR,CKPT) assoicated with the database(physical data files and logical tablespaces,tables etc, which stores the actual data).
<font face=courier>
ORCL1.WORLD =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = NMP)(SERVER = tree)
(PIPE = ORAPIPE))
(CONNECT_DATA = (SID = TEST))
)

orcl2.WORLD =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = NMP)(SERVER = tree)
(PIPE = ORAPIPE))
(CONNECT_DATA = (SID = SUP))
)
</font>
orcl1 and orcl2 are two net service names (aliases) on the same server tree connecting to two different SID`s SUP and TEST.
SUP and TEST are two instance names or SID`s associated with two diffrent databases?
Hope this helps. If doesn't try to follow the link and analyze.

[url]http://technet.oracle.com/doc/windows/server.804/a55913/apc.htm#449105[/url]







[Edited by sreddy on 01-23-2001 at 04:48 PM]

[sambavan]

Yes it kind of a confusion at times on what people mean by database and instance. Here are some of the past threads that is worth the spending some time to look
[url]http://www.dbasupport.com/forums/showthread.php?threadid=3421[/url]


[url]http://www.dbasupport.com/forums/showthread.php?threadid=3490[/url]


[url]http://www.dbasupport.com/forums/showthread.php?threadid=3781[/url]

Good luck.

Sam