NCL commands form three broad categories:

    o  Control commands (such as set ncl default, exit, help) enable
       the user to perform certain tasks within the NCL utility
       environment. These commands perform no network management
       functions.

    o  Database commands (such as, show, set, add, remove) modify
       or display characteristics for existing entities, but may not
       immediately affect the network configuration or operation.

    o  Action commands (such as create, delete, enable, disable)
       have an immediate impact on the operation of the network,
       often causing a state change to an entity. There are many
       entity-specific action commands (see the individual entity
       description sections for details). Any command that is not a
       control command or a database command is an action command.

    For descriptions of these verbs, refer to HELP <verb>.