dclock, dclockw, dcunlock - lock/unlock current data record for exclusive use
#include
Dclock attempts to lock the current data record for exclusive use
dflock(C-3), drlock(C-3),
dilock(C-3), dlopen(C-3),
dopen(C-3), drunlock(C-3)
Chapter 4, RMS Programming Guide DIAGNOSTICS Dclock and Dclockw return a value
of zero (0) if fcb is not an opened file block pointer or if locking the current
record would cause a deadlock.
Dcunlock cannot be used after a record is deleted since there is no current
record after a delete is performed. In this case, call drunlock(C-3).
DESCRIPTION
and returns immediately with a status code. If the current record
was locked successfully, dclock returns a positive value. If the
record could not be locked, perhaps because it was already locked
by another process, a zero value is returned.
Dclockw attempts to lock the current data record for exclusive
use and waits until the record can be locked before returning.
Dclockw normally returns a positive value.
Dcunlock unlocks a record that was locked with dclock or dclockw.
Fcb is the file block pointer returned by dlopen(C-3)
or
dopen(C-3).
These routines must be used with the RMS file functions that
update records in a multi-user environment. The RMS file
functions do not automatically lock files or records to prevent
simultaneous access to data by multiple processes.
These routines lock only one record at a time. It is permissible
to lock more than one record in the same RMSfile or to lock
records in more than one RMSfile. Note that locking more than one
record at a time may create a deadlock in which case the locking
is denied.
SEE ALSO
NOTES