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SET EXCLUSIVE*
Establish shared or exclusive USE of database files
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Syntax
SET EXCLUSIVE ON | off | <xlToggle>
Arguments
ON causes database files to be opened in exclusive (nonshared) mode.
OFF causes database files to be opened in shared mode.
<xlToggle> is a logical expression that must be enclosed in
parentheses. A value of true (.T.) is the same as ON, and a value of
false (.F.) is the same as OFF.
Description
In a network environment, SET EXCLUSIVE determines whether a USE command
specified without the EXCLUSIVE or SHARED clause automatically opens
database, memo, and index files EXCLUSIVE. When database files are
opened EXCLUSIVE, other users cannot USE them until they are CLOSEd. In
this mode, file and record locks are unnecessary.
When EXCLUSIVE is ON (the default), all database and associated files
open in a nonshared (exclusive) mode unless the USE command is specified
with the SHARED clause. Use EXCLUSIVE only for operations that
absolutely require EXCLUSIVE USE of a database file, such as PACK,
REINDEX, and ZAP.
When EXCLUSIVE is OFF, all files are open in shared mode unless the USE
command is specified with the EXCLUSIVE clause. Control access by other
users programmatically using RLOCK() and FLOCK().
SET EXCLUSIVE is a compatibility command and not recommended. It is
superseded by the EXCLUSIVE and SHARED clauses of the USE command.
Refer to the "Network Programming" chapter in the Programming and
Utilities Guide for more information.
Notes
. Error handling: Attempting to USE a database file already
opened EXCLUSIVE by another user generates a runtime error and sets
NETERR() to true (.T.). After control returns to the point of error,
you can test NETERR() to determine whether the USE failed.
Files Library is CLIPPER.LIB.
See Also:
FLOCK()
NETERR()
RLOCK()
USE
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