This is an Oracle Database Server Message. This can be generated by the Oracle Database when running any Oracle program.
This is in general the very first error message you get when you try to establish a connection to your oracle database. Often, it's a typographical error in your connexion string or in your tnsnames.ora file.
- Make sure that "TNSNAMES" is listed as one of the values of the NAMES.DIRECTORY_PATH parameter in the Oracle Net profile (SQLNET.ORA)
- Verify that a TNSNAMES.ORA file exists and is in the proper directory and is accessible (general tnsnames.ora location is: $ORACLE_HOME/network/admin/tnsnames.ora).
- Check that the net service name used as the connect identifier exists in the TNSNAMES.ORA file.
- Make sure there are no syntax errors anywhere in the TNSNAMES.ORA file. Look for unmatched parentheses or stray characters. Errors in a TNSNAMES.ORA file may make it unusable.
- Verify that "LDAP" is listed as one of the values of the NAMES.DIRETORY_PATH parameter in the Oracle Net profile (SQLNET.ORA).
- Verify that the LDAP directory server is up and that it is accessible.
- Verify that the net service name or database name used as the connect identifier is configured in the directory.
- Verify that the default context being used is correct by specifying a fully qualified net service name or a full LDAP DN as the connect identifier
- Verify that "EZCONNECT" is listed as one of the values of the NAMES.DIRETORY_PATH parameter in the Oracle Net profile (SQLNET.ORA).
- Make sure the host, port and service name specified are correct.
- Try enclosing the connect identifier in quote marks. See the Oracle Net Services Administrators Guide or the Oracle operating system specific guide for more information on naming.
You can train yourself with many books and get an advantage over your competitors
by developing a set of skills highly sought throughout the world. Niels Bohr saw an
expert as "a person who has found out by his own painful experience all the mistakes
that one can make in a very narrow field". So why not you? Be an expert!
To that aim, the first reference book I would suggest is "Oracle Database 11g The Complete Reference (Oracle Press)" by Kevin Loney. This internationally recognized Oracle expert was named Consultant of the Year by ORACLE Magazine in 2002. Also be aware that the 12c Oracle version is available on here : Oracle Database 12c The Complete Reference (Oracle Press).
In addition to that, let me suggest "OCP Oracle Certified Professional on Oracle 12c Certification Kit" as further reading in order to improve your skills and pass your first level certification.
Whether the above information has been helpful to you or not, we would appreciate reading your comments below. Also feel free to ask questions.
Some messages recommend contacting Oracle Support Services to report a problem. Please go here for more information : Oracle Support.