FOCUS FOR BEGINNERS : MFD

MASTER FILE DESCRIPTION INTRODUCTION THREE PRIMARY ATTRIBUTES of an MFD 1. FILE ATTRIBUTE 2. SEGMENT ATTRIBUTE 3. FIELD ATTRIBUTE DATE FORMAT OPTIONAL ATTRIBUTES IN MFD CHARACTERISTICS OF A MFD INTRODUCTION This chapter deals with how to describe a File to Focus so that it can use the
description while processing a report request.

As Focus can report both from its own database as well as from an external database , there must be a description for Focus that tells it of the nature of File (Fixed or Variable ) ,the Record names, the Field names, and the nature of the field ( Alpha Numeric, Integer , Packed etc..).

This description is stored in a separate file called a MASTER. In Mainframe Focus, there is an separate PDS where each member is a MFD. Each of which describes a particular file.

Generally the PDS is coded as **. MASTER. ** .

Let us learn on the characteristics of Master through this sample Master.

FILE=MAST, SUFFIX=FIX,
SEGNAME=EMPLOYEE,   ( ==> similar to a Record of IDMS.   )
FIELD = EMPLOYEE_ID , ALIAS= EID     , USAGE= I9, ACTUAL = I9 , $
FIELD = LAST_NAME     , ALIAS= LN     ,   USAGE= A10, ACTUAL = A10 , $
FIELD = FIRST_NAME    , ALIAS= FN      ,   USAGE= A15, ACTUAL = A15 , $
FIELD = DEPARTMENT , ALIAS= DEPT. , USAGE= D9.2, ACTUAL = D9,$

SEGNAME = PRSNL_INFO, SEGTYPE = S1,PARENT = EMPLOYEE ( ==> owner )
FIELD = SPOUSE_NAME, ALIAS = SN, USAGE = A25, ACTUAL = A25,$
FIELD = CHILDREN, , USAGE = I2, ACTUAL = I2,$

THE MFD HAS THREE PRIMARY ATTRIBUTES
· FILE ATTRIBUTE
· SEGMENT ATTRIBUTE
· FIELD ATTRIBUTE

FILE ATTRIBUTES : The FILE = <file name > specifies the name of the file . In case of   Mainframe Focus, the
member   name corresponds to the file name. ( Note :-- this is strictly not true but enough for our
purpose ).

The SUFFIX= specifies the type of the file to Focus. For a focus file it is FOC
for an external fixed formatted file it is FIX .   For an IDMS database it is IDMSR. SEGMENT ATTRIBUTES
                    The   SEGMENT = specifies the segment name.
The structure of an Focus database is Hierarchical .     So there can only be one Root segment, all others are descendants of it.
     RULES THAT GOVERN THE SEGMENT ATTRIBUTES.

· The first field of a segment must always have unique occurrences of   a value. E.g., SSN number.
· The occurrences of the segment are automatically sorted in an ascending order of the
first field .
· In case more than one field is desired   to be placed as the sort key, it is described as
SEGTYPE = S2.
In this case the first two fields are used for sorting.
· In case   the occurrences are to be sorted in an descending order, it is specified as
                SEGTYPE = SH2,
    In which case the segment occurrences are sorted and stored in an descending order
         of   the values of the first two fields.
· SEGTYPE = S0   Is valid . This and SEGTYPE=,, (No Type specification both are treated as that segment has no Key Fields).
· SEGTYPE = S0 Can be a Root segment whereas SEGTYPE=,, cannot be .
· SEGTYPE=,, is called as type blank segment.
· There are finer differences between these two types which will be discussed subsequently.
· SEGTYPE = U .     This defines a unique segment.   This is a child of the parent as defined in the MFD. However when this type is defined, There is only one occurrence of the child for every occurrence of the parent . This child segment is treated as if it was a logical continuation of the parent.

· The PARENT=   specifies the parent segment for the segment. In case this is omitted, the
   Parent defaults to the previous segment.
· Only the first field (ROOT SEGMENT) Can be without any parent.
· The segment name can be up to 8 characters long and of alphabetic characters A-Z. THE FIELD ATTRIBUTES
· FIELD = identifies the field name to Focus.
· The field name can be any alpha numeric character, but must begin with a Alphabet.
· ALIAS= is optional, and is similar to Synonym of an field name in IDMS.
· This ALIAS can be used in the FOCEXEC instead of the (generally) lengthy field names.
· If an alias is not defined then in the MFD, two commas must precede the USAGE= attribute.
· The USAGE = attribute is to describe to Focus how to display that particular data in report
    requests.
· The USAGE = <format> consists of three parts.
· 1. Field type
· 2. Field Length
· 3. Edit options.
· USAGE = A6MDY   ,   USAGE = I6
· Field type as in A, I, this is used to indicate the nature of the field such as Integer (I),
                 Alphanumeric (A) , etc....
· The field length is specified by   A6 , I9, etc....   note there are restrictions on the maximum length of the field for each Field type ,e.g., for Integer type it is 9.
· Edit options. the USAGE = A6MDY   ,   USAGE = I6E .Here the MDY tell Focus that it is a date field , Focus when displaying this field automatically inserts ‘/’ as 98/02/26 when it reads   980226 from the data base
· Other edit options are as ‘ L ‘ for inserting   leading   zeroes   etc... Date Format.

·   Focus has a extensive date format. A date in the YMD format can be
     displayed   as DMY format in the report just by changing the edit option of the field that is used to display it to NEW_DATE/A6MDYY= This will cause a date like 980227 to be displayed as 02/27/1998
· Other date conversions include displaying a date as Monday , December 30 1985,
· This would involve defining the date format to /A6MtrDYY.
· Actual Attribute.
· This describes the type of data as it actually exists in the data base or file. The source of this
information is the cobol FD statements. This ACTUAL= exists in the MFD only when describing
an external data to FOCUS, Focus data bases do not need it.

    There is an exclusive section for dates in FOCUS

OPTIONAL ATTRIBUTES IN MFD.

1.   Description attribute.   It is used to include a descriptive text for a field, and is ignored while
processing.   Up to 44 characters can be included in this.
E.g..   FIELD=UNITS,,USAGE=I6,ACTUAL=I6,
DESC==‘QUANTITY SOLD’, $
2. Title attribute.   Is used to supply an optional Column title instead of the field name.
E.g..   FIELD=DOB,,USAGE=I6YMD,ACTUAL=I6,
TITLE= ‘ Date of Birth’, $
3.    Missing attribute.    The default is OFF, if set to ON, Focus will distinguish a missing value
   from an internally entered blank or Zero. This is useful in reports where Counts or Averages are done.
When Missing is set to ON, and a count is done, all missing fields are excluded, similarly with the case of Averages.
4.     Field Type attribute.
Eg. FIELD=EMPLOYEE_ID,,USAGE=A6YMD,ACTUAL=A6,FIELDTYPE=I,$

This is used to create an index for a Field in a file. Note : Text fields cannot be
INDEXED , (i.e., FIELDS with USAGE=TX)

It is an internally stored and maintained table of values and the locations of these ,and helps in
retrieval.

An index is mandatory if
1. A segment is to be cross referenced, esp by JOINS,
2. Create certain alternate view files
3. Use a FIND function in MODIFY
4. Speed up retrieval for a given field.

5. HELP MESSAGE ATTRIBUTE :

E.g.. FIELD = EMPLOYEE_ID,,USAGE = A6YMD, ACTUAL = A6,
HELPMESSAGE=‘ XXXXX ....TEXT.... XXXXX’ ,$
Text is one line with up to 78 characters long.
This text is displayed in the type area of MODIFY or CRTFORM . This could also be used to specify acceptable values for the fields.

6. OCCURS ATTRIBUTE :
Eg.     OCCURS = n
                              field name
                              variable.
If it is    ‘n’   then ‘n’   describes the number of times that field occurs.

If field name, it names data set in the parent segment that is a counter containing the number
of occurrences of the descendent segments. ( Similar to COBOL's occurs depending on ..)

If variable, it indicates to Focus that the number of occurrences varies from record to record,
and Focus computes the number of occurrences from the field length.

In the MFD the entry for this would be as
SEGNAME=TWO,PARENT=ONE,OCCURS=2,$

7. POSITION ATTRIBUTE :
It is used to describe a structure in which a multiple number of occurrences of a field
occur in the middle of a record.

CHARACTERISTICS OF A MFD

1.     For Mainframe , the MFD must be always be 80 characters long.
2.     All must be in capitals, except the contents of TITLE and DESC attributes.
3.      The contents of an single specification can spill over to as many lines and is ended by the
           delimiter ‘ $ ‘.

Click here to learn on the basic verbs used in FOCUS