This error appears when the process of starting up a dedicated server process failed and it could be either because the executable could not be found or the environment isn’t set up correctly.

Turn on tracing at the ADMIN level and re-execute the operation. Tracing can be set by adding following clause in listener.ora file and restarting the listener:-

TRACE_LEVEL_listener=admin

Verify that the ORACLE Server executable ($ORACLE_HOME/bin/oracle) is present and has execute (6751) permissions enabled. Ensure that the ORACLE environment is specified correctly in LISTENER.ORA. The Oracle Protocol Adapter that is being called may not be installed on the local hard drive. Please check that the correct Protocol Adapter are successfully linked.