/CHECK[=(option[,...])]
  /NOCHECK                 (D)

  Specifies conditions to be checked at execution time.  Controls
  whether the system checks the validity of numeric digits or
  PERFORM statements, indexes, subscripts, reference
  modification, and the OCCURS DEPENDING ON depending item for
  specific run-time errors.  If you specify a qualifier option,
  the default options do not change unless they are individually
  modified.

  You can select one or more of the following options:

  [NO]PERFORM         Verifies that PERFORM statement  rules  are  met.
                      The default is NOPERFORM.

  [NO]BOUNDS          Verifies the range of  subscripts  and  reference
                      modifiers.  The default is NOBOUNDS.

  [NO]DECIMAL         Validates numeric digits when using display
                      numeric items in a numeric context.  The default
                      is NODECIMAL.

  [NO]DUPLICATE_KEYS  Verifies that the duplicate key specification
                      for indexed file keys in the source program
                      matches the duplicate key specification in the
                      physical file.  The default is NODUPLICATE_KEYS.

  ALL             Same as /CHECK without any options.

  NONE            Same as /NOCHECK.  Default if /CHECK is not used.

  Specifying /CHECK=PERFORM controls whether the system checks PERFORM
  statements.  Incorrect use of PERFORM statements can produce
  unpredictable results and, when used with the PERFORM option, causes
  the system to generate a run-time message and abort the program.

  Specifying /CHECK=BOUNDS controls whether the system checks the range
  of subscripts, indexes, and the depending item in the DEPENDING ON
  phrase of the OCCURS clause. The system generates a run-time message
  and aborts the program if it detects one of these errors:

     If DEPENDING ON is not specified and a subscript or index is
     greater than the upper bound or less than or equal to zero

     If DEPENDING ON is specified and a subscript or index is
     greater than the depending item or less than or equal to zero

     If a depending item is less than the low bound or greater
     than the upper bound, and either a subscripted or indexed
     item references a table or a group containing the table is
     referenced as a sending item

  Specifying /CHECK=DECIMAL controls whether the system checks for
  numeric characters when using numeric display items in a numeric
  context and generates an error if any digit is invalid (not
  numeric).

  Specify /CHECK=DECIMAL to validate data produced by other systems
  that might use a different internal representation for numeric data.
  You can also use this qualifier option to detect logic errors in
  programs that result in text data being moved to numeric data items.

  Specifying /CHECK=DECIMAL produces extra instructions to perform
  these checks, which may result in slightly larger images and
  slightly longer execution times than the /CHECK=NODECIMAL qualifier
  option.

  The default, /NOCHECK, is the equivalent of /CHECK=NONE.

  Specify /CHECK with the /NOOPTIMIZE qualifier, as optimization can
  make finding error found by /CHECK more difficult.