DF_FILE_MODE

Level

Table

Supported by

All Drivers

Type

Flag of bits, temporary

Access

Read / Write

Values

Any iored combination of the following modes:

DF_FILEMODE_DEFAULT
DF_FILEMODE_NO_REREAD
DF_FILEMODE_NO_LOCKS
DF_FILEMODE_NO_EDITS
DF_FILEMODE_NO_DELETES
DF_FILEMODE_NO_FINDS
DF_FILEMODE_NO_CREATES

Predefined combinations of the above:

DF_FILEMODE_READONLY
DF_FILEMODE_SINGLE_USER

Remarks

Access modes affect operational characteristics of a table.

Constant	Value	Meaning
`DF_FILEMODE_DEFAULT`	0	No access restrictions on the table.
`DF_FILEMODE_NO_REREAD`	1	Reread on the table is not allowed.
`DF_FILEMODE_NO_LOCKS`	2	The table will not be locked.
`DF_FILEMODE_SINGLE_USER`	3	Table is opened in single user mode.
`DF_FILEMODE_NO_EDITS`	8	Records in the table cannot be edited.
`DF_FILEMODE_NO_DELETES`	16	Records in the table cannot be deleted.
`DF_FILEMODE_NO_FINDS`	32	Records in the table cannot be found.
`DF_FILEMODE_NO_CREATES`	64	Records in the table cannot be created.
`DF_FILEMODE_READONLY`	91	Table is opened in read-only mode.

DF_FILEMODE_READONLY combines DF_FILEMODE_NO_REREAD, DF_FILEMODE_NO_LOCKS, DF_FILEMODE_NO_EDITS, DF_FILEMODE_NO_DELETES, and DF_FILEMODE_NO_CREATES.

DF_FILEMODE_SINGLE_USER combines DF_FILEMODE_NO_REREAD and DF_FILEMODE_NO_LOCKS.

You can make your own combinations of access restrictions by using the bitwise or operator (ior) to combine individual modes. For example, if you want to place a restriction on table MyTable that no records can be created or updated, you would use the following code fragment:

Set_Attribute DF_FILE_MODE Of MyTable.File_Number to ;
(DF_FILEMODE_NO_EDITS iOr DF_FILEMODE_NO_CREATES)

It is expected that the only settings an average DataFlex programmer will need are DF_FILEMODE_DEFAULT and DF_FILEMODE_READONLY. Since the DataSet and DataDictionary classes support smart file mode, setting the file mode is not needed to tune for lock performance. Setting file mode to read-only for reporting can improve report speed.

Function OverallTotal Returns Number
    Number nTotal
    Integer iOrgMode

    Get_Attribute DF_FILE_MODE of OrderHea.File_Number to iOrgMode
    Set_Attribute DF_FILE_MODE of OrderHea.File_Number to DF_FILEMODE_READONLY
    Clear OrderHea
    Find Gt OrderHea By 1

    While (Found)
        Add OrderHea.Order_total to nTotal
        Find GT OrderHea By 1
    End

    Set_Attribute DF_FILE_MODE Of OrderHea.File_Number to iOrgMode
    Function_Return nTotal
End_Function

The sample function above sets the file mode of the OrderHea table temporarily to read-only and then calculates the total amount of all orders.