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global ORACLE_SID in UNIX and concurrent oracle user sessions

From: Boivin, Patrice J <>
Date: Sat, 02 Sep 2000 15:28:55 -0300
Message-Id: <>

Imagine you have a UNIX server with multiple instances on it.

You have one user called "oracle".

To work on either instance, you ensure that you set the global variable ORACLE_SID=3Dinstance; export ORACLE_SID


I open one terminal window.
I set ORACLE_SID=3Dinstance1; export ORACLE_SID, then start an import = into one
database, and let it run.

I open a second terminal window because I want to work on the second instance.
I set ORACLE_SID=3Dinstance2, export ORACLE_SID.

Does the import in the first session still point to instance1, or is it = now
trying to import data into the second instance because the value of the global variable has changed?

I am asking because while restoring two instances on one server, I = ended up
with one instance's control file pointing to files belonging to the = second
instance. Thankfully the imported tablespaces in the second instance = did
not already exist in the first, so there was no overlap. I just = dropped
them and re-imported them into the right database. I also made sure = that
the import was the ONLY session open on the server during the import.

It is possible that I did an import into the wrong instance, but now I = am
wondering what happens when you change a global variable like that on-the-fly.

I am not a UNIX guru obviously.

I asked the sa here but he didn't think changing the global variable = would
affect other UNIX processes that have already started. I am wondering though if import might not be reading that variable each time it is to = begin
importing another schema, as a matter of course.

Patrice Boivin
Systems Analyst (Oracle Certified DBA)

Systems Admin & Operations | Admin. et Exploit. des syst=E8mes
Technology Services        | Services technologiques
Informatics Branch         | Direction de l'informatique=20
Maritimes Region, DFO      | R=E9gion des Maritimes, MPO

E-Mail: <>=20 Received on Sat Sep 02 2000 - 13:28:55 CDT

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