Performs a specified action when an error equal to or greater than the
specified error severity level or a CTRL/Y interrupt occurs. Use only
in command procedures.

Format
 ON event THEN [$] command

Additional information available:

Parameters

event
 One of the following events:

 +--------------+-------------------------------------------+
 | WARNING      | Return status of warning ($SEVERITY       |
 |              | equals 0) occurs.                         |
 +--------------+-------------------------------------------+
 | ERROR        | Return status of error ($SEVERITY equals  |
 |              | 2) occurs.                                |
 +--------------+-------------------------------------------+
 | SEVERE_ERROR | Return status of error ($SEVERITY equals  |
 |              | 4) occurs.                                |
 +--------------+-------------------------------------------+
 | CONTROL_Y    | CTRL/Y character occurs on SYS$INPUT.     |
 +--------------+-------------------------------------------+

command
 Any valid DCL command line.