Maintaining Your Data Model › Creating User-Defined Field Types › Specifying Basic Attribute Values

Specifying Basic Attribute Values

This panel shows the attributes of the field type (DTX, as used for the first example) and highlights the two main columns where you can change its values.

The first column, Allow user entry, indicates how the field type attributes will be displayed when a field of this type is shown for editing on the Edit Field Details panel; the second column, Initial values, is for specifying the initial default values allowed for that field type.

For example, you would select and change the values for the Internal data type of the DTX attribute as follows:

For Allow user entry, O means the Internal data type attribute is to be displayed with a fixed value; I means it can be modified; and H means it is to be hidden altogether.

For Initial value, P means you want Internal data type to have the value of Packed numeric.

The following description of the attributes and default values shown for a field type on the Edit Field Type panel will explain further how you define a new field type.

• Field type—The field type for which the attribute values are to be specified.
• Text—A short description of the field type, for example, "8-character date field."
• Right hand side text—the default right hand side text for fields of this type.
• Internal data type—The system data type of the field to be stored on a database file. It can have one of these values:

• Internal length—The number of bytes used to store a field in files. Fields with decimal positions are entered as: total number of digits, number of decimal places. For example, for a field to contain 999.99, the length would be 5.2.
• External data type—System data type of field to be displayed on device files. It can have one of these values:

• External length—The number of characters or digits in a field on a panel or print file. Fields with decimal positions are entered as: total number of digits, number of decimal places. For example, for a field to contain 999.99, the length would be 5.2.
• Keyboard shift—Specifies which keyboard shift is allowed for the field on panel files. It can have one of these values:

For more information on keyboard shift values, refer to the IBM DDS Reference manual.

• Lowercase—specifies whether the field values may be in lowercase. Lowercase applies only to alphanumeric fields. It can have one of these values:

• Check valid system name—specifies whether any value entered for the field must be a valid i OS system name. A valid system name must start with a letter, no more than 10 characters long, and must contain only letters, digits or one of these characters: "-", "#", "$", or "@".
• Mandatory fill—specifies whether an entry if any must be made for every character of the field. This can have one of these values:

• Modulus check 10/11—specifies whether any value entered for the field must meet a modulus 10 or 11 check as specified by the DDS CHECK keyword. Modulus check applies only to numeric fields. This can have one of these values:

• Allow value mapping—specifies whether value mapping will be implemented for the field. If value mapping is 'Y', you must specify an Int/ext function and an Ext/int function. If no value mapping is required, you can still specify an Ext/int function to perform other validation.

This can have one of these values:

• Int/ext len conv—specifies how external length is to be determined. This can have one of these values:

• Int/ext function—This is the function that is to convert the internal value to external value for the field. It must be a function attached to the *Field attribute types file.
• Ext/int function—This is the function that is to convert the external value to internal value for the field and validate it if required. It must be a function attached to the *Field attribute types file.