ORA-12541 with connections made to an 11.2 RAC DB through a SCAN Listener but the Listeners are all up

(Doc ID 2085951.1)

Last updated on DECEMBER 06, 2015

Applies to:

Oracle Net Services - Version 11.2.0.1 and later
Information in this document applies to any platform.

Symptoms

Connections to an 11.2 RAC Database using SCAN are either failing consistently or 50% of the time with ORA-12541 "no listener"
This is the case despite confirming that the Listeners are all running on the designated addresses and a tnsping against the connection alias reveals no differences in the address used by the Client

Cause

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