Command table operations can signal these conditions:
Summary: This condition is signaled by make-command-table when you try to create a command table that already exists.
Summary: This condition is signaled by functions such as find-command-table when the named command table cannot be found.
Summary: The error that is signaled when a function tries to add a command that is already present in a command table to that command table.
Summary: A condition that is signaled when the command you are looking for is not present in the command table.
Summary: A condition that is signaled when the command you are looking for is not accessible in the command table.
Summary: The class that is the superclass of the previous four conditions. This class is a subclass of error .
Common Lisp Interface Manager 2.0 User's Guide - 20 Sep 2011