Normally, when you define the record fields, each defined field represents a single piece of data in the record. This allows your programs access to all of the record data.

There are times when you want to process two or more adjoining fields. For example, if you have a last name field, first name field and initial field and you want to sort the records by name, you would sort the three separate fields--last name, first name and initial.

To simplify this process, you can define an additional data field, FULL_NAME, which can consist of the three fields. When you define the FULL_NAME field, the starting position would be the first position of the last name and the length would be the total number of characters in the three fields. Then, when you want to sort or print the full name, you need only refer to one field, the FULL_NAME field.

For example, if you have the following fields defined:

Example 16-11 Defining Fields

You would define the field FULL_NAME as in the example below:

Example 16-12 Defining Fields

Redefining fields becomes very useful when you need to set up unique key fields for ARS indexed files.

KEY FIELDS

If you are creating an ARS indexed file, you will be designating one or more data fields as KEY FIELDS. ARS indexed files require at least one key field.

When you use the CREATE procedure to create an ARS indexed file, you will be prompted for a primary key field and alternate key fields.

SheerPower supports keys of 4096 bytes in length.

Key fields contain unique data which enables programs to locate records very quickly. For example, the customer number field could be a key field because all the customer numbers in all the records would be different. This type of key field is called a UNIQUE KEY FIELD.

DUPLICATE KEY FIELDS contain unique types of data but the data might be found in more than one record in the file. Any defined or redefined field can be designated as a key field. However, it is best to use fields that normally will contain unique data as key fields. Common practice is to set up the first field as a key field.

A key field can be defined which consists of two or more fields. If the fields which make up this key field are not adjoining (i.e. one after the other), this is called a SEGMENTED KEY FIELD. Key fields consisting of two or more fields, whether segmented or not, must have a length that equals the total length of all the segments that make up the key field.

SheerPower can extract records using a segmented key.

A record has the following field definitions:

Example 16-13 Defining Key Fields

To define a SEGMENTED KEY that consists of CREATE_DATE plus CUSTOMER_ID, you would define another field, DATE_CUST_KEY, that starts at the first position of the first segment of the key with the length being the sum of the lengths of all of the segments:

Example 16-14 Defining Using a Segmented Key

To extract using this key:

EXTRACT STRUCTURE customer, FIELD date_cust_key: partial key “20020101” . . END EXTRACT

The above statement would extract all CUSTOMER records created on 1/1/2002.

To modify an existing data field in a structure definition, enter SETUP and select the structure to be modified. See Section 16.1.1, Entering SETUP for details on how to enter SETUP.

Click on [Properties].

The currently defined data fields will be displayed.

Click on the data field that you want to modify . The [MODIFY] button will then become available.

Example 16-15 Modifying an Existing Field

When you click on [MODIFY] the Field Definition window will appear. All input fields, except name, can be modified. See Section 16.3.1, Data Field Definitions for details on the various data field information options.

Caution must be taken if you modify the field starting position and field length as your new starting position and length may overlap other data in the record. Other fields may also need to be modified for correct starting positions and lengths.

If you need to delete an existng data field in a structure definition, enter SETUP and select the structure to be modified. See Section 16.1.1, Entering SETUP for details on how to enter SETUP.

Click on [Properties].

The currently defined data fields will be displayed.

Click on the data field that you want to delete and the [Delete] button will become available.

Example 16-16 Deleting an Existing Field in SETUP

You will then be prompted to confirm the deletion of this data field:

Example 16-17 Deleting an Existing Data Field

Choosing NO will return you to the Field Definition window.

Choosing YES will immediately delete the selected field.

Note Deleting a data field contained in the file does not reposition following data fields.

In the example we deleted the field XCODE (see example above). We now have a record layout like this:

Example 16-18 Deleting an Existing Field in SETUP

Note that field ZIP starts at position 132 for a length of 9 and field REP_CODE starts at position 145 for a length of 10. There is a gap between the two fields where the deleted field had been.

When you need to view or print the record layout/definition you have several options.

Enter SETUP and select the structure to be viewed. See Section 16.3.1, Data Field Definitions for details on how to enter SETUP.

How the data fields will be presented to you is controlled by selections in the Structure Definition window, under the Data Field Definitions heading. You have the options to sort by name, description, position and the length of what is to be shown.

Example 16-19 Viewing Field Definitions

Sort By: Description Name sorts by the field names Description sorts by the descriptions that have been entered for the fields Position sorts the fields in record layout by their starting position in the record Length Description Short Displays field name, description, first position, length, data type Medium Displays field name, description, first position, length, occurances, last position, data type, print mask, semantics Full Displays field name, description, first position, length, occurances, last position, data type, print mask, semantics, prompt, heading, help, screen mask, validations

Clicking on [Properties] will bring up the Fields window where you can see the report on screen.

Clicking on [View/Print] in the Fields window will bring the field information report up in Notepad where you can then do normal Notepad functions, including printing.

Structure security controls access levels for read, write, update and delete activities.

Enter SETUP, select the structure (see 15.1.1 Entering SETUP and 15.2 SETUP Structure Definition) and click on [Security].

Example 16-20 Structure Security

The following information will then be displayed on the window:

Example 16-21 Structure Security

The security level is a single letter in the range of A to Z. Security level A is the highest level of security. Security level Z is the lowest level of security.

The default value for the security and access levels is ‘N’, normal. You may optionally assign a different security level to the structure and then for both the definition and the dataset you can assign various security levels for read, write, update and delete accesses.

Read/ Write/ Update/ Delete Access Levels

The access level is a single letter in the range A to Z. A is the most restricted access level. Z is the least restricted. When an attempt is made to read, write, update or delete a record from this structure, SheerPower will compare the structure security level to the corresponding access level. If the access level is lower than the structure security level, the request will not be allowed.

For example:

Structure Read Access Security Level Level Access K R Allowed because R is > K K E Denied because E is < K K K Allowed because K = K

Clicking on [Security] again will remove the security information from the window.