Keyed record commands are generally used only to maintain functionality in maps created in older versions of the ECMap software. Keyed record I/O is used with dBase III files, and most current ECMap users take advantage of the power and flexibility of ODBC-compliant databases.
When you select the Keyed Record I/O up arrow in the Parameters section of the Rule Command - New window, the Keyed I/O window displays.
Database – the DBASE FILE check box is permanently checked.
Keyed I/O Command – to use this option, the files must already exist. Choose from:
Keyed Read – reads the next record in the file.
Keyed Write – writes or appends the record to the file.
Keyed Rewrite – rewrites the record in the file.
File Location, File Name, and File Record – see the file containing the field designated as the key field. The value of the key must have been previously set by an assignment rule. If you choose the Select button, the Directories/Mailboxes window displays. You can drag a directory, a file, or a record from the Directories/Mailboxes window and drop it onto the File Record text box, and the other two File text boxes are populated. If you drag and drop a file, information is entered in the File Location, File Name, and Index File text boxes. You can also double-click a record on the Directories/Mailboxes window and it is entered in the text box, but you must always drag and drop directories and files.
Index File – the name of the dBase index file being used.
Status Variable – a memory variable that holds the error condition returned by the Keyed I/O. This memory variable can be used in an If Condition. (See the If Condition for instructions on how to use this variable to determine whether or not the record was found.) If you choose Select, the Memory Variables window displays. You can drag a memory variable from the Memory Variables window and drop it onto the Status Variable text box.
Keyed Field Value – choose from:
Memory Variable – displays next to the Rule Command window. Double-click a memory variable and the program automatically enters it in the bottom text box below the Keyed Field Value text box.
Record/Field – displays next to the Rule Command window. Double-click a field and the program automatically enters it in the bottom text box below the Keyed Field Value text box.
System Variable – displays next to the Rule Command window. Double-click a system variable and the program automatically enters it in the bottom text box below the Keyed Field Value text box.
Constant – enter a value in the text box on the Constant Value window that displays and select OK. The value is automatically entered in the bottom text box below the Keyed Field Value text box.
