You can use a logical file to prevent a field in a physical file from being viewed. This is accomplished by describing a logical file record format that does not include fields you do not want the user to see. For more information about this subject, see Describing Logical File Record Formats.
You can also use a logical file to prevent one or more fields from being changed in a physical file by specifying, for those fields you want to protect, an I (input only) in position 38 of the DDS form. For more information about this subject, see Describing Field Use for Logical Files.
You can use a logical file to secure records in a physical file based on the contents of one or more fields in that record. To secure records based on the contents of a field, use the select and omit keywords when describing the logical file. For more information about this subject, see Selecting and Omitting Records Using Logical Files.