TNS-12518: TNS:listener could not hand off client connection TNS-12536: TNS:operation would block TNS-12560: TNS:protocol adapter error TNS-00506: Operation would block IBM/AIX RISC System/6000 Error: 11: Resource temporarily unavailable

An application owner was getting the error TNS-12537 while trying to establish connection to a database.

The following errors were found in the listener alert log of an AIX server hosting about 10 database instances.

TNS-12518: TNS:listener could not hand off client connection
TNS-12536: TNS:operation would block
TNS-12560: TNS:protocol adapter error
TNS-00506: Operation would block
IBM/AIX RISC System/6000 Error: 11: Resource temporarily unavailable

oerr utility doesn't show much information.

oratest@db060b8:/ $ oerr ora 12537
12537, 00000, "TNS:connection closed"
// *Cause: "End of file" condition has been reached; partner has disconnected.
// *Action: None needed; this is an information message.



further investigation revealed that the value of maxuproc is set to too low for user "oratest" on the AIX server.

# lsattr -E -l sys0 | grep maxuproc
maxuproc        2048                                 Maximum number of PROCESSES allowed per user      True

For a database that has so many database instances with several client connection requests, we had to adjust this value to a higher one (double in this case).

# chdev -l sys0 -a maxuproc=4096

# lsattr -E -l sys0 | grep maxuproc
maxuproc        4096                                 Maximum number of PROCESSES allowed per user      True


Issue resolved!