hi sureshy,


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let's say you wanted 2 different instances on one server.

Would that mean that you would have to install oracle software for each instance on the server with 2 oracle_homes?
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No, you don't have to, but it still possible if other version is necessary.

To create another database with the same server is:
above all, shutdown the original db and backup
1. copy and rename the original initSID.ora(newinitSID.ora)
change the directories for control file and archive log files.
change the db_name(NEW_DB).
2. source the ORACLE_SID=NEW_DB
3. startup nomount pfile=newinitSID.ora
4. issue the command to create the new database the usual.
create database "NEW_DB"
DATAFILE .... SIZE 300MB
LOGFILE GROUP 1.....
GROUP 2....
MAXDATAFILES 1024
MAXLOGFILES 248
blah....blah....
5. run catalog.sql and catproc.sql
6. your db must be ready to open.

Add tnsnames for the new database, and same as for listener

then you can connect
system/manager@oldtnsname
and
system/manager@newtnsname

without sourcing the ORACLE_SID.

I hope I don't miss something.