The  VALID_FOR_DATATRIEVE_IF  field  attribute  clause   causes   VAX
  DATATRIEVE  to validate value assignments to a field.  VAX DATATRIEVE
  refuses to assign a value to a field if that value is not accepted by
  this validation expression.

1  –  Parameter

  dtrvi_quoted_string

       VAX DATATRIEVE source text forming a validation expression.

2  –  Syntax Rule

  The quoted strings  must  form  a  valid  VAX  DATATRIEVE  validation
  expression.    The  CDDL  compiler  does  not  check  the  validation
  expression for correct syntax.

3  –  Usage Notes

   o  Only VAX DATATRIEVE can interpret these  validation  expressions.
      Other language processors ignore their presence.

   o  You can use 8-bit characters in CDDL quoted strings.

4  –  Example

  In the following example, the VALID FOR DATATRIEVE IF  clause  causes
  VAX  DATATRIEVE  to  accept  only  positive  integers  for  the field
  TRANSACTION_COUNT.

  TRANSACTION_COUNT       DATATYPE IS UNSIGNED WORD
                          VALID FOR DTR IF
                              "TRANSACTION_COUNT > 0".