- The database user id or password is wrong. This can usually be diagnosed by looking in the x_err.log where the X_RUN parameters are listed.
- The ORACLE listener or database is not started. To check whether the listener is started use the following command on the database server
To see whether the database is started use the following command on the database serverps -ef | grep $ORACLE_SID
- The ORACLE listener is not configured correctly. Refer to Oracle support and manuals for possible causes.