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MultiValue Files

A data storage structure.

Description

A MultiValue file is a data storage structure created using Caché global variables. It is a fundamental part of MultiValue database architecture, corresponding to the UniVerse or UniData hashed data or dictionary file.

A MultiValue file is created using the CREATE.FILE verb. It is cataloged in the VOC file as a global variable, and can be concurrently accessed by multiple processes. You can use the FILEINFO function to determine the pathname of the global variable.

The OPEN statement opens a MultiValue file and returns the filevar local variable. This filevar is used for all subsequent MVBasic operations on this MultiValue file:

  • WRITE is used to write data to a MultiValue file.

  • READ is used to read data from a MultiValue file.

  • DELETE is used to delete a data record from a MultiValue file.

  • CLEARFILE is used to delete all data records in a MultiValue file.

  • SELECT is used to read the record identifiers from a MultiValue file into a select list. These record identifiers can then be individually read using the READNEXT statement.

  • CLOSE is used to close a MultiValue file, resetting filevar to null.

  • The FILEINFO function is used to determine the status of filevar and other information about a MultiValue file.