ORA-12560: TNS:protocol adapter error in Oracle

ORA-12560: TNS: protocol adapter error


SQL> connect scott/tiger as sysdba
ORA-12560: TNS:protocol adapter error

On Checking on Oracle Sites:

A generic protocol adapter error occurred.

Check addresses used for proper protocol specification. Before reporting this error, look at the error stack and
check for lower level transport errors. For further details, turn on tracing and re-execute the operation.
Turn off tracing when the operation is complete.


1. This error will come if Listener is not up or problem in tnsnames or database is not up.

2. Check the listener status by executing.

lsnrctl status

3. Check the tnsnames entry in tnsnames.ora


4. Check the database status is up running by checking the service in windows or process in Unix.

On Windows:
Start --> Run--> type "services.msc"
Select the OracleService name, Right Click, Start.

On Unix or Linux:
ps -ef pmon*

5. Check the environment variable of ORACLE_HOME, PATH, TNS_ADMIN and ORACLE_SID.

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