In this post, you’ll learn more about the Oracle ErrorTNS-04012: Unable to start Oracle Connection Manager instance. with the details on why you receive this error and the possible solution to fix it.
Oracle Error Description
TNS-04012: Unable to start Oracle Connection Manager instance.
Reason for the Error TNS-04012: Unable to start Oracle Connection Manager instance.
Cause: CMCTL was unable to start the Oracle Connection Manager instance. Some of the possible reasons include: cmadmin not present in ORACLE_HOME/bin, Invalid parameter in configuration repository, wrong parameter values, or log directory not present.
How to fix the Error TNS-04012: Unable to start Oracle Connection Manager instance. ?
You can fix this error in Oracle by following the below steps
Action: 1. Check whether log directory is present, and is writable. Log directory can be found at ORACLE_HOME/network/log, or as specified by the LOG_DIRECTORY parameter in CMAN.ORA.
2. Turn on logging or tracing to get more information about this error.
3. Correct any parameter errors (or mismatched paranthesis), and retry starting Oracle Connection Manager.
4. If the problem persists, contact Oracle Support Services.