The following Microsoft Basic example demonstrates the use of the FATS 
indexing commands:
REM FATS 02.30
REM (c) GCS Software, Udo Gertz 1993-1998
REM
REM Test program (Microsoft Basic / Quick Basic Compiler)
REM
REM Reindex the test data file customer.dat.
REM
REM 19-03-2009 U.Gertz
REM -------> Activation of FATS Cache
REM
REM By default the cache functionality is deactivated. It can be activated
REM with the 
"Y" Auto Refresh command.
REM
REM If you want to reorganize a index file for example, you can activate
REM the cache algorithm with the commands "Y\5" or "Y\106", then build the
REM entire file and finally restore the original status (e.g. "Y\0", "Y\2").
REM The operation can be speed up for 30 times.
REM
REM FATS does not perform writes to the operation system until its cache is
REM full and the least-recently-used algorithm controlling the I/O buffer
REM cache selects a buffer for reuse. FATS never writes to the index file
REM unless the cache buffers are entirely filled during a single command.
REM In addition, FATS does not perform the reset disk operations that cause
REM the operation system to flush its cache buffers to the disk. It does not
REM close and reopen the file each time it physically expands in order to
REM flush the directory structure.
REM When using this command, you cannot assume that any of your updates have
REM been written to the disk until you either perform a close operation or
REM execute the command Write Page Map (W).
REM
REM Use "Y\106" instead of "Y\5" in an network environment.
REM
CALL FATSBASIC( "Y\5", ERRORCODE%, RECNO&, KEYLEN% )
REM -------> Open data file
OPEN "R", #1, "CUSTOMER.DAT", 128
FIELD #1, 1 AS DELETEDMARK$,_
5 AS CUSTID$,_
25 AS NAME$,_
25 AS JOB$,_
25 AS STREET$,_
5 AS ZIP$,_
20 AS CITY$
REM -------> Create index file
CALL FATSBASIC( "C\CUSTOMER.KEY\5;25\4\A\1", ERRORCODE%, RECNO&, KEYLEN% )
IF ERRORCODE% <> 0 GOTO ENDE
REM ========================================================================
REM Re-Indexing
REM ========================================================================
RECORDS& = 0
DO
GET #1, RECORDS& + 1
IF EOF(1) THEN
EXIT DO
END IF
RECORDS& = RECORDS& + 1
IF DELETEDMARK$ = " " THEN
REM "BK" Build Keys
REM
REM This command inserts the primary keys of the specified
REM data record ("RecNo") into the index file. The number
REM of keys included in the command string must equal the
REM number of primary keys you specified in the Create
REM Indexfile (C) command.
REM
REM This command corresponds to the command Insert Keys (IK)
REM except that FATS does not perform writes to the operation
REM system until its cache is full and the least-recently-used
REM algorithm controlling the I/O buffer cache selects a buffer
REM for reuse. FATS never writes to the index file unless the
REM cache buffers are entirely filled during the operation.
REM All other FATS commands will update the index file before
REM returning to the calling program (if this feature had not
REM been disabled with the Auto Refresh command).
REM
REM The syntax of the command string:
REM
REM szCmnd = "BK\{RecNo}\{FileNo}\{KeyStr1}[\{KeyStr2}[\{KeyStr3}]]"
REM
REM RecNo Record number
REM
REM FileNo File number
REM
REM KeyStr# Key value
CMND$ = "BK\" + STR$(RECORDS&) + "\1\"
CMND$ = CMND$ + RTRIM$(CUSTID$) + "\" + RTRIM$(NAME$) + "\" + RTRIM$(JOB$) + "\" + RTRIM$(ZIP$ + CITY$)
ELSE
REM "DL" Manipulate Deleted List
REM
REM The record numbers of deleted data records are taken up
REM by FATS automatically with the command Delete Record (D)
REM to a list of the data records that already have been
REM deleted, so that the command Insert Record (I) can
REM possibly reuse these, before the data file must be
REM extended. This list is administered according to the
REM principle last in, first out, i.e. the record deleted
REM last is reused as next.
REM
REM This command allows you to manipulate this list by
REM inserting and deleting of record numbers. Because free
REM space in the data and index files is reclaimed and reused
REM by FATS automatically as records are deleted and added,
REM this command is normally not needed, but it can be useful
REM for reindexing data files containing deleted records.
REM
REM Note that using this command in conjunction with the
REM commands "Insert Record" and "Delete Record" can result
REM in corrupted data files, incorrect query results, and
REM program failures.
REM
REM The syntax of the command string:
REM
REM szCmnd = "DL\{RecNo}\{GetSetFlag}\{FileNo}"
REM
REM RecNo Record number
REM
REM GetSetFlag Possible values:
REM
REM G Remove a record number from the list
REM of deleted records. If there are no
REM entries in the list this command will
REM return the number of the next available
REM record in the data file. If there are
REM entries in the list, the record number
REM of the last deleted record will be
REM returned.
REM
REM This command is automatically called by
REM FATS when the Insert Record (I) command
REM is used.
REM
REM S Add a record number ("RecNo") to the
REM list of deleted records.
REM
REM This command is automatically called by
REM FATS when the Delete Record (D) command
REM is used.
REM
REM FileNo File number
CMND$ = "DL\" + STR$(RECORDS&) + "\S\1"
END IF
CALL FATSBASIC( CMND$, ERRORCODE%, RECNO&, KEYLEN% )
IF ERRORCODE% <> 0 THEN EXIT DO
LOOP WHILE NOT EOF(1)
ENDE:
REM --------> Close index file
CALL FATSBASIC( "K\1", ERRORCODE%, RECNO&, KEYLEN% )
CLOSE #1
END
© 2008 
GCS Software, Udo Gertz
