Options

2=Change

Change the attributes of a Field for the Entry.

3=Copy

Copy the Field to create a new Field for the Entry.

4=Delete

Delete the Field from the Entry.

5=Display

Display the attributes of the Field.

The Field-information consists of:

The primary attributes of a Field are:

Field name

 

A case sensitive name of maximal 30 characters that serves as a unique identification of the Field inside the Entry. This name must start with an uppercase and may not contain any blanks.

Sequence number

A five-digit number that uniquely determines the position of the Field in the Entry.

Offset

When an ITP Model uses the Entry all Fields of the Entry are returned in one block of data to the Model. The offset determines where in this block of data the information of the Field starts, relative to the start of the block (thus the smallest possible offset is 0).

Data type

The data type of the Field. This can be TEXT (T), PACKED (P), ZONED (Z), BINARY (B) or Unicode (W). ITP does not support all DDS field types: refer to "Supported DDS field types" for more information.

Length

The length in bytes of the Field.

Decimal positions

Number of decimal positions in the Field. Only used if the data type of the Field is numeric (PACKED, ZONED or BINARY)

Alignment

Alignment of the Field. This can be either left aligned (L) or right aligned (R). Only used if the data type of the field is not numeric (TEXT or Unicode)

Field generation

Can be either "Automatically" (A), "Manually" (M) or "Automatically but changed" (blank). This tag indicates the way in which the Field was created.

The extended attributes of a Field are automatically filled in when an Entry is generated and contain extra information from the File definition. The extended attributes are not used when a Field is created manually. The extended attributes are:

File field name (DDS name)

The original DDS name of the Field in the database file the Entry was generated over.

Sequence number file field

The original sequence number of the Field in the database file the Entry was generated over.

Offset file field

The original offset of the Field in the record of the database file the Entry was generated over. The smallest offset possible is 1 to indicate the Field started on the first position of the record.

Sequence number of key field

If the database file field was a key field in the database file the Entry was generated over, this sequence number indicates its position relative to the other key fields in the file. 0 indicates that the database file field was not a key field.

Entry Creation and Generation contains more information on the relation between the Field definitions and the database file definitions that an Entry can be created over and about the data retrieval mechanism ITP uses. From the point of view of an ITP Model, Fields are the objects that contain the information from the database: it is by using a Field in the ITP Model that the content of the field is used. From the point of view of the technique of retrieving data from the database, Fields only determine how the ITP Model must interpret the data that was returned to the ITP Model.

The data retrieval mechanism returns a block of data. The record length attribute of the Entry determines the size in bytes the block of data is supposed to have. After the ITP Model receives the block of data and a Field is used in the Model the data is interpreted using the attributes of the Field. Only then the ITP Model takes a "Field length" number of bytes from the block of data returned starting at the "Field offset" and translates it according to the "Field type" attributes of the Field.

The record length attribute of the Entry is the most important in the data retrieval mechanism. On Entry generation this attribute is retrieved from the record length of the file definition the Entry was generated over. When the Entry is manually created or Field definitions of the Entry are changed after generation, the record length should reflect the Field definitions of the Entry. The exact formula is: record length = (offset of the last field + length of the last field). In general it is possible to have bytes returned to the ITP Model that are not used in any Field of the Entry. Option "19=Calc. Offsets" on the "Work with Entries" may be used to calculate the record length of the Entry and the offsets of the Fields based on the sequence numbers and the length of the field. This option assumes that there are no unused bytes in the record, and moves the fields by adjusting the offsets of the fields so that they start directly behind the previous Field.