dclock, dclockw, dcunlock - lock/unlock current data record for exclusive use
#include Dclock attempts to lock the current data record for exclusive use 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.
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 isDESCRIPTION
SEE ALSO
NOTES
no current record after a delete is performed. In this case, call
drunlock(C-3).