This topic discusses the ways you can use logical files to secure data.
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.
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.
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.