Re: Starting 2 instances of the same Oracle database on the same machine

Giri wrote:
> Is it possible to start 2 instances of the same database on the same
> machine.
> 1) I create an Oracle database with SID, say, 'myOracle' and start it
> (login as SYS user and start the database)
> 2) Now, is it possible to start another instance of 'myOracle' with the
> first instance up?
> I'm asking this question because, I was running some scripts which
> resulted in 2 instances of the same Oracle database running and am not
> sure how Oracle allowed a user to start 2 instances! As far as I know
> it should not be possible. Can anybody explain this?
> Thanks,
> Girish

select * from global_name;

perhaps one is like myOracle.yourdomain.com and the other is myOracle.yourdomain.ishosed.

Also, some platforms may do weird things with case, ie, myoracle v. myOracle.

The answer is very platform/version dependent, in general David is right. On unix, you have to be able to have a shared area, which is named with a key that is a hash of the SID. On some versions of Oracle (certainly O7), it was possible to have two different SIDs hash to the same value, so the second one would get shared memory errors when you bought it up. I've even seen this in O9, when an improperly started and killed Oracle left an unremoveable shared segment out there, so trying to bring any second instance up was impossible without rebooting (because as far as resources were concerned, it would be the third instance).

For examples on what to test and what really needs to be changed to use the same SID on the same machine see
http://groups.google.com/group/comp.databases.oracle.server/browse_thread/thread/56cd67f8bca9b710/a7862664bd34d0ed?lnk=st&q=&rnum=1&hl=en#a7862664bd34d0ed and
https://metalink.oracle.com/metalink/plsql/f?p=200:27:272954429977175958::::p27_id,p27_show_header,p27_show_help:652563.999,1,1 .

So of course, it is important to specify platforms and versions. And don't even think about using multiple instances with the same SID in production!

jg

-- 
@home.com is bogus.
http://www.zefrank.com/giveaway2/