What Is in a Master File?

In this section:

Improving Readability
Adding a Comment
Editing and Validating a Master File

How to:

Specify a Declaration

A Master File describes a data source using a series of declarations:

A data source declaration.
A segment declaration for each segment within the data source.
A field declaration for each field within a segment.
Declarations for other objects that can be optionally added to the data source description, such as FILTER, DEFINE, COMPUTE, and SORTOBJ definitions.

The specifications for an Access File are similar, although the details vary by type of data source. The appropriate documentation for your adapter indicates whether you require an Access File and, if so, what the Access File attributes are.

Syntax: How to Specify a Declaration

Each declaration specifies a series of attributes in the form

attribute = value, attribute = value, ... ,$

where:

attribute: Is a Master File keyword that identifies a file, segment, or field property. You can specify any Master File attribute by its full name, its alias, or its shortest unique truncation. For example, you can use the full attribute FILENAME or the shorter form FILE.
value: Is the value of the attribute.

A comma follows each attribute assignment, and each field declaration ends with a dollar sign ($). Commas and dollar signs are optional at the end of data source and segment declarations.

Each declaration should begin on a new line. You can extend a declaration across as many lines as you want. For a given declaration you can put each attribute assignment on a separate line, combine several attributes on each line, or include the entire declaration on a single line.

For more information on data source declarations, see Identifying a Data Source.
For more information on segment declarations, see Describing a Group of Fields.
For more information on field declarations, see Describing an Individual Field.

Note: In a Master File, the attribute name must be in English. The attribute value can be in any supported national language.

Improving Readability

Begin each attribute assignment in any position. You can include blank spaces between the elements in a declaration. This makes it easy for you to indent segment or field declarations to make the Master File easier to read. To position text, use blank spaces, not the Tab character.

You can also include blank lines to separate declarations. Blank spaces and lines are not required and are ignored by the application.

Example: Improving Readability With Blank Spaces and Blank Lines

The following declarations show how to improve readability by adding blank spaces and blank lines within and between declarations:

SEGNAME=EMPINFO, SEGTYPE=S1 ,$
  FIELDNAME=EMP_ID, ALIAS=EID, USAGE=A9 ,$

SEGNAME=EMPINFO, SEGTYPE=S1 ,$
  FIELDNAME = EMP_ID, ALIAS = EID, USAGE = A9 ,$

SEGNAME=EMPINFO,SEGTYPE=S1,$
  FIELDNAME = EMP_ID, ALIAS = EID, USAGE = A9 ,$

Example: Improving Readability by Extending a Declaration Across Lines

The following example extends a field declaration across several lines:

FIELDNAME = MEMBERSHIP, ALIAS = BELONGS, USAGE = A1, MISSING = ON,
  DESCRIPTION = This field indicates the applicant's membership status,
  ACCEPT = Y OR N, FIELDTYPE = I,
  HELPMESSAGE = 'Please enter Y for Yes or N for No' ,$

Adding a Comment

You can add comments to any declaration by:

Typing a comment in a declaration line after the terminating dollar sign.
Creating an entire comment line by placing a dollar sign at the beginning of the line.

Adding a comment line terminates the previous declaration if it has not already been terminated. Everything on a line following the dollar sign is ignored.

Comments placed after a dollar sign are useful only for those who view the Master File source code. They do not appear in graphical tools. For information about providing descriptions for display in graphical tools using the REMARKS or DESCRIPTION attribute, see Identifying a Data Source, and Describing an Individual Field.

Example: Adding a Comment in a Master File

The following example contains two comments. The first comment follows the dollar sign on the data source declaration. The second comment is on a line by itself after the data source declaration.

FILENAME = EMPLOYEE, SUFFIX = FOC ,$ This is the personnel data source.
$ This data source tracks employee salaries and raises.
SEGNAME = EMPINFO, SEGTYPE = S1 ,$

Editing and Validating a Master File

After you manually create or edit a Master File, you should issue the CHECK FILE command to validate it. CHECK FILE reads the new or revised Master File into memory and highlights any errors in your Master File so that you can correct them before reading the data source.

The CHECK FILE PICTURE command displays a diagram illustrating the structure of a data source. You can also use this command to view information in the Master File, such as names of segments and fields, and the order in which information is retrieved from the data source when you run a request against it.

For more information, see Checking and Changing a Master File: CHECK.