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.

Additional information available:

ParameterSyntax RuleUsage NotesExample

 dtrvi_quoted_string

      VAX DATATRIEVE source text forming a validation expression.

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

  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.

 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".