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How to fix Informix® error -951 when clients try to connect

Question & Answer


When client connections try to reach the Informix instance, the error -951 (User username is not known on the database server/User is not known on remote host) is raised, avoiding clients to connect.


You see errors like this in the online.log file:

13:14:57 Get Shadow Password for user [username] failed!
13:14:57 Check for password aging/account lock-out.
13:14:57 listener-thread: err = -951: oserr = 0: errstr = username@::ffff:[]: Incorrect password or user username@::ffff:[] is not known on the database server.

Several symptoms can cause such behaviour:

  1. SQLHOSTS file mispelled entries;
  2. DBSERVERNAME or DBSERVERALIASES onconfig parameters have no related entries in the SQLHOSTS file;
  3. NIS or LDAP servers misconfiguration or maintenance;
  4. INFORMIXDIR filesystem and/or its subdirectories have wrong permissions or ownership;
  5. User is locked or expired;
  6. oninit binary is somehow damaged or have wrong permissions.


Here's a list of things to check when facing such a problem:

1) Double-check the SQLHOSTS file for missing or mispelled entries regarding the DBSERVERNAME and DBSERVERALIASES onconfig parameter values;

2) Validate with the OS staff changes in the LDAP or NIS servers;

If none of the above were causing the issue, check the INFORMIXDIR filesystem for proper permissions and/or ownership:

1) Collect an ls -ltrR output from the INFORMIXDIR filesystem and compare its contents with the $INFORMIXDIR/etc/IIFfiles file;

2) Check for onwership too;

If the contents of the ls -ltrR diverges from the $INFORMIXDIR/etc/IIFfiles file, consider doing one of following:

1) Fix manually the missing permissions or ownership of every file/subdirectory;

2) Copy the INFORMIXDIR filesystem from another validated non-productive host;

3) Restore this filesystem from backup;

4) Re-install the Informix Server binaries.

In any of the options above, make proper backups of critical files like the onconfig, sqlhosts and ixbar files.

Important: these are just a few probable causes for this problem, if this document didn't solve your issue, consider calling IBM Informix Technical Support for assistance.

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Document Information

Modified date:
16 June 2018