Sometimes You can get “ORA-12638: Credential retrieval failed ” error.
ORA-12638: Credential retrieval failed
Details of error are as follows.
ORA-12638: Credential retrieval failed
Cause: The authentication service failed to retrieve the credentials of a user.
Action: Enable tracing to determine the exact error.
SQLNET.ORA
To solve this problem, change SQLNET.AUTHENTICATION_SERVICES= (NTS) parameter to SQLNET.AUTHENTICATION_SERVICES = (NONE) on sqlnet.ora under $ORACLE_HOME/NETWORK/ADMIN directory.
The old value is as follows.
SQLNET.AUTHENTICATION_SERVICES= (NTS)
The new value should be as follows.
SQLNET.AUTHENTICATION_SERVICES= (NONE)
Do you want to learn more details about RMAN, then read the following articles.
RMAN Tutorial | Backup, Restore and Recovery Tutorials For Beginner Oracle DBA