1. Seeing this wait increase and very high, which it never shows up as a wait.
  2. Users don't get back to the database when they make requests - it takes a while before they land on the database and when they do, they get an immediate resolution to query/insert/etc.
  3. It really appears there's an issue with the users getting confirmed before querying - this is just a guess based on some reading. Microsoft provides nothing on this wait that I can find.
  4. The normal volume for users dropped 99% when this wait took off.
  5. Developers seeing "you are not authorized to access microsoft iis" on their end - but we've checked disk space on all servers, which is fine.

What we've done:

  1. Restarted all servers - SQL and web.
  2. CPU, memory, disk all seem fine on SQL Server.
  3. This wait continues to increase.
  4. Error log doesn't show any abnormal behavior.

Overview of issue: people will run a query on the website, we don't see it on the back-end until much later, when I do see it, it runs immediately and they get their result. There seems to be a delay from the intermediate server to the database server, possibly related to authentication (a guess based on this wait). It's possible this wait is completely unrelated, but it continues to increase and I've never seen this.


This is an issue external to SQL Server. You should check that your authenticating AD servers for this machine are working correctly, and that you are not accidentally attempting to authenticate to AD in another data center (presuming that you have one). Additionally look for problems on the AD servers, such as high CPU utilization.

For more details on this wait type look at https://www.sqlskills.com/help/waits/preemptive_os_authenticationops/

| improve this answer | |
  • 1
    I have seen this due to inadvertent routing of authentication traffic to an AD domain controller in another data center as identified via a network trace. The trace will identify the DC(s) involved for further troubleshooting. – Dan Guzman Oct 15 '16 at 10:54

We have faced same problem and I found that wait 'PREEMPTIVE_OS_AUTHENTICATIONOPS' is occurring with another wait type 'ASYNC_NETWORK_IO'.
It clearly means that SQL Server is waiting for requesting application to consume data and send back 'received' signal. In my case it was IIS which is malfunctioning and not consuming data. So I have fixed IIS and problem is resolved.

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.