Windows | ORA-12560: TNS:protocol adapter error

Hi guys

Not many DBAs prefer Windows for their Oracle databases. Linux is most preferred by most of them & most of the DBAs I know setup the bash profile under Oracle user to setup the environment during each logon to the server.

Our legacy business application database runs on Windows 2003 & trust me, we never had a single database crash (Other than the physical hardware failure that forced us to recover the database once). Depending upon how huge the database and application, the choices for hosting the Oracle database differ from one business to other.

We decided to upgrade our Oracle 10g 10.1.x.x 32Bit database to 11g R2 & as usual I have replicated the environment using my home semi-server class desktop, before the Production environment at work.

Installed 10g 32Bit, created the database using dump export file (The total size of the database is less than 7GB, hence I avoided the hectic RMAN backup and restore part)

  1. Configured RMAN against the new database & made full backup for archive logs and database.
  2. Installed 11g 64Bit database (Software Only installation)
  3. Created a new Windows Service using oradim
  4. Restored the database from RMAN backups & upgraded the database to 11g

So far so good. I had to restart the computer & after rechecking the database was up and running, tried to access the instance using sqlplus & was presented with

ORA-12560: TNS:protocol adapter error


I setup ORACLE_SID=SID at the CMD window & sqlplus was happy after that.

Usually, Windows doesn’t need environment variables set exclusively for the database as Windows registry takes care of it. This is very efficient when the box has only one database running. If you have more than one database or multiple Oracle homes, the scenario changes.

In addition to, Oracle always looks for the executable based on the PATH information it reads. For example my box has 10g,11g,12c database software installed without any databases created during the installation time.

Let us consider the scenario like I didn’t re-order the PATH entries after the latest installation of 12c & try to open SQL or RMAN. The call will find the executable from 12c path entry BIN as default, and a beginner could have enough confusions due to it.

In my case, I needed my 10g instance first, hence I moved the 10g folder as the 1st entry for Oracle products, and once I finished with 10g moved 11g home folder to the 1st position.


Anyway, after confirming the path settings, my immediate attention was towards registry, as Oracle services completely depend upon the registry values for each service registered.

To my utter surprise, found the 11g Service entry didn’t have ORACLE_SID string created during the instance creation using ORADIM.exe


Oracle 11g has a huge bug list and interim patches those should be applied before moving to Production instance. I really don’t know whether the missing ORACLE_SID string entry was due to one of such bugs.

So I stopped the Oracle service, added ORACLE_SID string entry with the value for my database


Restarted the service & sqlplus connected to the instance happily without setting up the environment variable like set ORACLE_SID=SIDNAME


While the easiest solution is to setup both ORACLE_HOME, ORACLE_SID when someone wants to use the sqlplus or RMAN exclusively as a part of the database access, the above method is a definite way to deal with “ORA-12560: TNS:protocol adapter error”




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