I’m hunting down more or less a sporadic error that sometimes our users get during initial attempt to connect to Oracle server.

Some facts:
– this error was never raised on NT4 domain; it was first noticed shortly after we migrated all our clients to Active Directory
– we don’t use OS authentication, all users are using classic Oracle accounts
– we do have SQLNET.AUTHENTICATION_SERVICES = (NTS) in the sqlnet.ora on all client machines
– so far, the only workaround is to remove SQLNET.AUTHENTICATION_SERVICES = (NTS) from sqlnet.ora on all worstations
– another observation is that we usually get several trace files generated in UDUMP, such as:

Dump file d:\oracle\admin\ora\udump\orcl_ora_3920.trc
Tue Aug 21 08:18:17 2007
ORACLE V10.2.0.2.0 - Production vsnsta=0
vsnsql=14 vsnxtr=3
Oracle Database 10g Enterprise Edition Release 10.2.0.2.0 - Production
With the Partitioning, OLAP and Data Mining options
Windows Server 2003 Version V5.2 Service Pack 1
CPU                 : 4 - type 586, 4 Physical Cores
Process Affinity    : 0x00000000
Memory (Avail/Total): Ph:2488M/8190M, Ph+PgF:4528M/10044M, VA:1411M/3071M
Instance name: orcl
Redo thread mounted by this instance: 1
Oracle process number: 36
Windows thread id: 3920, image: ORACLE.EXE (SHAD)
opiino: Attach failed! error=-1 ifvp=00000000

– Metalink Note:399727.1 “Opiino: Attach Failed! Error=-1 Ifvp=0″ Written Many Times Per Minute In Udump File And ORA-12500 In Listener.log” doesn’t apply to our situation, because there is only one database running on the server. Also, we do not observe ORA-12500 in the listener.log – this is weird.

Based on Event Log message at the client:

Warning - LsaSrv - SPNEGO (Negotiator) - Event 40961 
The Security System could not establish a secured connection with the server 
ldap/server.domain.com/domain.com@domain.com.  No authentication protocol was available.

…I would say that this is an OS issue, not an Oracle Net bug. Google search revealed that Event 40961 is usually a consequence of miss-configured DNS (missing reverse lookup entry for the server), but not in our case. If I’ll ever find the culprit for the error I’ll update this thread with a solution.