Function RLock() Foundation
Locks current record for SHARED write access.
RLock() --> lSuccess
The return value of RLock() is .T. (true) if the current record in a work area was locked for SHARED write access. Otherwise .F. (false) is returned.
The database function RLock() locks a record for write access and prevents write access by other work stations. This capability is required in a multi-user application in network environment when a user is changing data in a record which might be in use at the same time by another user. When the record could be locked, RLock() returns the value .T. (true). The record is then only available for read access to other users until the record lock is released with DbUnlock() or a command like UNLOCK or CLOSE.
A record must be locked with RLock() when file operations change a record. Commands like @..GET, RECALL, DELETE or REPLACE and the function FieldPut() belong to this group.
After each call of RLock() only one attempt is made to lock the data record in a work area. When the function is used without the alias operator, the attempt to lock the record occurs in the current work area.
When relations are defined (using SET RELATION or DbRelation()) for the file, the dependent files may also need to be locked. Automatic locking of all dependent records does not occur using RLock().
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