Defining fields manually

This chapter describes the use of DEFINE FIELD command, which allows you to define the fields in a file. For the full syntax, follow that link.

Defining fields

After you create and initialize a Model 204 file, use the DEFINE command or the IFDFLD Host Language Interface function to establish the names and types of the fields in the file.

The format of the DEFINE command is:

Syntax

DEFINE FIELD name [(attribute [,[attribute ...]]) | WITH [attribute][,[attribute ...]]]

where:

name is a 1 to 255 character name that must begin with a letter and can contain any alphanumeric characters, including spaces, except:

 ?? ?$ ?& @ (or an alternative delete character) # (or an alternative flush character)

attribute is a member of the list in Field attributes.

If you specify the ORDERED attribute, you can follow it with a list of qualifying parameters that designate the type of ordering and the space utilization characteristics of the Ordered Index. See the discussion of the ORDERED attribute in ORDERED and NON-ORDERED attributes.

Example

In the following example the field CUSTID is named and given the ORDERED CHARACTER attribute:

DEFINE FIELD CUSTID ORDERED CHARACTER

Specify as many field attributes as needed from Field attributes. For each attribute pair shown in the list, only one of the alternatives can be specified; conflicting attributes, such as KEY and NON-KEY, cannot be used together in a single description.

Note

Every attribute has a default value. Therefore, you only need to specify the attribute if it is not the default.

When to use the FIELD keyword

The keyword FIELD is required before field names that begin with the word FIELD, PRINTER, or DATASET. It is optional with other field names. If FIELD is specified, only one field can be defined or redefined per command. For example:

DEFINE FIELD POLICYHOLDER DEFINE POLICYHOLDER

Each example above defines a field with the name POLICYHOLDER. The following example defines a field with the name FIELD LOCATION:

DEFINE FIELD FIELD LOCATION

Defining sort key, hash key, and record security fields

The DEFINE command cannot be used to define sort key fields, hash key fields, or record security fields. These fields can be defined only with the INITIALIZE command, described in INITIALIZE command, and the appropriate parameter settings.

Field attributes

The attributes listed in the following tables are introduced in Field Design, along with a summary of the rules follow in assigning them. A number of the attributes have additional optional attributes (in particular, see the ORDERED attribute) that can be specified with the DEFINE FIELD command, which are also described in Field Design.

Indexing attributes

The overall effect of the defaults is that, unless specified, the field is not indexed.

Indexing field attributes with the DEFINE command

Attribute	Abbreviation	Default
ORDERED CHARACTER NON-ORDERED	ORD CHAR NORD	NON-ORDERED
ORDERED NUMERIC NON-ORDERED	ORD NUM NORD	NON-ORDERED
KEY NON-KEY	- NKEY	NON-KEY
FRV NON-FRV The ORD attribute is preferable; shown for compatibility.	- NFRV	NON-FRV
[NUMERIC] RANGE NON-RANGE Obsolete; supported for compatibility.	NR NNR	NON-RANGE

Datatypes

In most cases, only one of these may be specified on any field (see the UTF attributes). The default is STRING

Data type attributes with the DEFINE command

Attribute	Abbreviation	Notes
STRING	STR
BINARY	BIN
BINARY-LARGE-OBJECT CHARACTER-LARGE-OBJECT	BLOB CLOB	must have Table E enabled
FLOAT	FLT	must have LEN specified
DATETIME	DT
UTF-8 UTF-16	UTF8 UTF16	Must be used in conjunction with the BLOB or CLOB attribute
VISIBLE INVISIBLE	VIS INV

Data Content Attributes

Data content field attributes with the DEFINE command

Attribute	Abbreviation	Default
UPDATE IN PLACE UPDATE AT END	UP UE	UPDATE IN PLACE
LENGTH m	LEN m	No preallocated length
OCCURS n	OCC n	No preallocated occurrences
PAD character		Character = X'00'
DEFERRABLE NON-DEFERRABLE	DEF NDEF	DEFERRABLE
AT-MOST-ONE EXACTLY-ONE REPEATABLE	ONE EXONE REPT	REPT (except in 1NF files), or inside an RFG (where it is EXONE)
CODED NON-CODED	COD NCOD	NON-CODED
FEW-VALUED MANY-VALUED	FV MV	MANY-VALUED

Field constraints

More than one constraint may be set on a field. Foe example, if you only want to accept integer values between 5 and 99, then you can code:

DEFINE FIELD fieldname WITH INTGE 5 INTLE 99

Field constraint attributes with the DEFINE command

Attribute	Abbreviation	Notes
UNIQUE NON-UNIQUE	UNIQ NUNIQ	NON-UNIQUE
LEVEL	LEV	See Security
Field length constraints
LENGTH-EQ	LEQ
LENGTH-GE	LGE
LENGTH-LE	LLE
Integer value constraints (validate contents against permissible integer value)
INTEGER-GE	INTGE
INTEGER-GT	INTGT
INTEGER-LE	INTLE
INTEGER-LT	INTLT
Float length constraints (validate contents against permissible float value)
FLOAT-GE	FLTGE
FLOAT-GT	FLTGT
FLOAT-LE	FLTLE
FLOAT-LT	FLTLT

Concatenated fields

Concatenated field attributes with the DEFINE command

Attribute	Abbreviation	Notes

Automatic fields

Automatic field attributes with the DEFINE command

Attribute	Abbreviation	Notes

Defining a field inside a Repeating Field Group

Linking a field to a Repeating Field Group with the DEFINE command

Attribute	Abbreviation	Notes
FIELDGROUP	FG	If not the last attribute specified, requires an ' AND ' after it

OCCURS and LENGTH clauses

The variables n and m specified for OCCURS and LENGTH must be decimal numbers between 1 and 255. The PAD character can be specified in decimal, hexadecimal (X'xx'), or character (C'c') form, and can take on any value equivalent to a number between 0 and 255.

All preallocated fields (fields that have an OCCURS clause) must be defined before any records are added to the file.

Note: After records are loaded, you can add a preallocated field definition only by reinitializing the file, defining all the fields-including the new preallocated field-and reloading the records. Non-preallocated field definitions can be added at any time.

Defining field retrieval attributes

If you do not know if a field will be used in retrievals, you can define it initially as NON-KEY, NON-ORDERED, and NON-RANGE. Then, you will be able to monitor the use of the field in FIND statements using information written to the journal data set and redefine it as KEY, NUMERIC RANGE, or ORDERED when necessary.

For details, see Monitoring field retrievals in FIND statements.

Implementing the date-time stamp feature (DTS)

The date-time stamp feature in Model 204 lets you can easily discern when a record in a file was last changed. The date-time stamp feature is supported for ONLINE and BATCH204.

See Setting Up the Date-Time Stamp Field for the steps the System Manger must take before this feature is used,
and Adding a Date-Time Stamp field for rules on using the feature.

Preventing definition of new field names

Model 204 permits a user to define new fields at any time. This is an advantage in some applications, because it enables the file to evolve beyond its original definition. If your site does not want users to add new field names, reset the FOPT parameter to X'01' from its default value of X'00'. This file option causes Model 204 to issue the following response, when a user issues a DEFINE command:

*** M204.1261: NEW FIELD NAMES NOT PERMITTED

Regardless of the setting of the FOPT parameter, users with file manager privileges (see the PRIVDEF parameter) can define new fields at any time. See the discussion in FOPT parameter for more detail.