The vutil function in which you can add, delete, or modify keys in an existing Vision file is available from the Update Key tab.
The tab contains the following options:
| Option | Description |
|---|---|
| File name | The Vision file in which to modify the keys. |
| Operation | Select the required operation to perform on the file. |
| Key number | The key number to add, delete, or modify |
| Quiet mode (-q) | Check this option to suppresses the warning message that is generated informing you that the file is modified in place. |
| Define Key Information | When adding or modifying a key, you need to supply the number of segments, and the size and offset of those segments within the key. |
| List | Displays the command line equivalent of the selected options. See Modifying Keys in an Existing Vision File for details on the command line utility. |
| Start | Click Start to run the operation. If Quiet Mode is unchecked, a confirmation message displays in the bottom pane. Enter Y in the Input field and click Send to continue with the operation. |
Due to the nature of these operations, you should not perform them on a Vision file without backing it up beforehand. Any failure during the modification of the key structure could leave the file in an unrecoverable state, and requiring you to revert to a backup.
Before performing any of the modification operations, the Vision file is marked as broken, with a 97 sub-code (98,97 file status). Upon successful completion of the operation, this code is removed.
If a new or modified key is specified to not allow duplicate key values, and duplicate key values are found when the key is indexed, the setting will be overridden and the key will allow duplicate key values.
When altering the key structure of a file to allow duplicate key values, be aware that data may not be retrieved in the order that you expect when using that key. To distinguish duplicate key values, a unique value is assigned to each record containing the duplicate data. Usually, this happens as the record is written to the file, and so records can be retrieved using this data, in chronological order. By introducing duplicate keys on an existing file, the unique values must be assigned en masse, in the order that the records currently sit in the file; therefore, retrieving records using the key will not necessarily return them in the order in which they were written.