ORA-29701: unable to connect to Cluster Manager

Problem:

Client connections to the RAC DB are getting errors -> ORA-01114 & ORA-29701

The CSSD daemon uses /tmp/.oracle directory to establish a local socket for communication with local clients such as RDBMS instances.  So you might want to ensure this was not removed by accident.

Solution: 

Reboot the node. 

Unfortually, the location of /tmp/.oracle cannot be changed (at least for 10g RAC)  or how this behaves in terms of the socket file location.  Therefore, this is something your Organization needs to be aware of.