Pavan DBA's Blog

Let me share an experience with you people which I faced 2 weeks back…

I got an email from application team stating they are unable to connect to database and getting below error

TNS-12518: TNS: listener could not hand off client connection

I immediately checked the listener status on the database server (My database is of 11.2.0.1 version on Windows platform) and it is up and running fine.As per regular troubleshoot check, the solution would be to trace the connection

ORA-12518: TNS:listener could not hand off client connection
 
Cause: The process of handing off a client connection to another process failed.

Action: Turn on listener tracing and re-execute the operation. Verify that the listener and database instance are properly configured for direct handoff. If problem persists, call Oracle Support.
But, before tracing, I checked the listener log file and observed below message

TNS-12560: TNS: Protocol adapter error
TNS-00530: Protocol adapter error
64-bit Windows Error: 53: Unknown error
TNS-12518: TNS: listener could not hand off client connection
TNS-12571: TNS: packet writer failure
TNS-12560: TNS: Protocol adapter error
TNS-00530: Protocol adapter error
64-bit Windows Error: 54: Unknown error
I tried reloading the listener and after restarting, users were able to connect for sometime. But after few minutes again same issue(error) occurred.

Finally after searching few sites, I got to know that this would be because of large size of listener log file.

If the listener.log is greater than 4GB in size, the listener may fail to start on Windows platforms.

This is a bug (bug no 9497965) on windows and as a resolution, I moved the file to other location, so that Oracle will created a new log file. From that moment, there are no issues observed in the user connectivity.

So, next time if you face this issue, check your listener log file size.

Please refer to MOS DOC ID 9497965.8 for more details….

Note : As per the MOS doc, this bug will not reproduce in 11.1.0.7 patch 29 or higher, but I am still wondering because my version is 11.2.0.1. It might have not fixed now….