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MFS

Description

SI.MFS

All files that contain indexed fields are monitored by SI.MFS.  If this MFS detects that a change has been made to an indexed field, it creates a transaction that is later used to update the appropriate index. SI.MFS also traps certain retrieval calls such as READNEXT and fulfills them from an index, rather than directly from the file.

 QUICKDEX.MFS and RIGHTDEX.MFS

If installed, QUICKDEX.MFS and RIGHTDEX.MFS monitor all writes, selects, and deletes against a file. During a write, these MFSs update a hidden record in the file, maintaining a sorted list of keys for records in the file.

During a SELECT and READNEXT, QUICKDEX.MFS and RIGHTDEX.MFS simply read this hidden record, providing almost instantly a sorted list of record keys. At the same time, the MFSs hide the record by removing its name from any select lists generated by the user.

DICT.MFS

Two major functions are rolled into DICT.MFS.  First, the MFS monitors writes to any dictionary (any file with a name beginning with the characters "DICT."), and calls the dictionary compiler whenever an F or S type record is written to the file.

Second, DICT.MFS examines all records being written to look for indexing flags. If any are found (for example, if the sixth field is set, a Btree index has been established for that field), DICT.MFS calls additional system routines used to create an index for that field.

DICT.MFS differs from other MFSs in OpenInsight in that it is installed "on the fly." The mere presence of the trigger characters "DICT." at the front of a file name causes the ATTACH process to install DICT.MFS onto the file automatically. Other MFSs must be installed explicitly.