Using different fields: field-level sensitivity

Field-level sensitivity applies the same kind of security for fields within a segment that segment sensitivity does for segments within a hierarchy: An application program can access only those fields within a segment, and those segments within a hierarchy to which it is sensitive.

Field-level sensitivity also makes it possible for an application program to use a subset of the fields that make up a segment, or to use all the fields in the segment but in a different order. If a segment contains fields that the application program does not need to process, using field-level sensitivity enables the program not to process them.

Example of field-level sensitivity

Suppose that a segment containing data about an employee contains the fields shown in the following table. These fields are:

  • Employee number: EMPNO
  • Employee name: EMPNAME
  • Birthdate: BIRTHDAY
  • Salary: SALARY
  • Address: ADDRESS
Table 1. Physical employee segment
Employee Number Employee Name Birthdate Salary Address
EMPNO EMPNAME BIRTHDAY SALARY ADDRESS

A program that printed mailing labels for employees' checks each week would not need all the data in the segment. If the DBA decided to use field-level sensitivity for that application, the program would receive only the fields it needed in its I/O area. The I/O area would contain the EMPNAME and ADDRESS fields. The following table shows what the program's I/O area would contain.

Table 2. Employee segment with field-level sensitivity
Employee Name Address
EMPNAME ADDRESS

Field-level sensitivity makes it possible for a program to receive a subset of the fields that make up a segment, the same fields but in a different order, or both.

Another situation in which field-level sensitivity is very useful is when new uses of the database involve adding new fields of data to an existing segment. In this situation, you want to avoid re-coding programs that use the current segment. By using field-level sensitivity, the old programs can see only the fields that were in the original segment. The new program can see both the old and the new fields.

Specifying field-level sensitivity

You specify field-level sensitivity in the PSB for the application program by using a sensitive field (SENFLD) statement for each field to which you want the application program to be sensitive.