Oracle Errors Interview Question:

ORA-12514: TNS:listener does not currently know of service requested in connect descriptor?

Submitted by: Administrator

Cause: The listener received a request to establish a
connection to a database or other service. The connect
descriptor received by the listener specified a service name
for a service (usually a database service) that either has
not yet dynamically registered with the listener or has not
been statically configured for the listener. This may be a
temporary condition such as after the listener has started,
but before the database instance has registered with the
listener.
Submitted by: Administrator