The Oracle message known as “ora-12154” may be the most common error experienced by Oracle users. Luckily, the frustration of so many previous users has prompted some fairly straightforward solutions to the issue.

The Problem

When you receive this error, it means that the Oracle client has failed to connect with the listener on the desired server.  In Oracle’s own words:

“A connection to a database or other service was requested using a connect identifier, and the connect identifier specified could not be resolved into a connect descriptor using one of the naming methods configured. For example, if the type of connect identifier used was a net service name then the net service name could not be found in a naming method repository, or the repository could not be located or reached.”

There can be many possible causes for this problem, which is why it can be tricky to solve. Users may have to test more than one method before identifying the source of the ORA-12154.

The target server could have temporarily gone down, which is likely if the issue is occurring across multiple PCs after attempting to access the network. Connection issues could also be the culprit, or the destination name may not match the input address.

It should be noted that if the ORA-12154 error is identifying in a set along with an additional error titled “TNS-03505: failed to resolve name,” the problem should have occurred before the server was located.

The Solution

For those using local naming (TNSNAMES.ORA file), Oracle recommends the following actions:

  • 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.
  • 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.

For those using directory naming:

  • 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.

And, finally, for those using easy connect naming:

  • 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.

Consulting an experienced firm for their expertise can be vital when dealing with the large-scale implementation of data management systems.

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