DbLock

       #include <db_cxx.h>

       int
       DbLock::put(DbLockTab *lt);

       unsigned int
       DbLock::get_lock_id();

       void
       DbLock::set_lock_id(unsigned int);

       DBLock::DbLock(unsigned int);
       DBLock::DbLock();
       DBLock::DbLock(const DbLock &);
       DbLock &DBLock::operator = (const DbLock &);

DESCRIPTION

       The  DB  library  is  a  family of classes that provides a
       modular programming interface to transactions and  record-
       oriented  file  access.   The library includes support for
       transactions, locking, logging and file page  caching,  as
       well  as  various  indexed  access  methods.   Many of the
       classes (e.g., the file page  caching  class)  are  useful
       independent of the other DB classes, although some classes
       are explicitly based on other classes (e.g.,  transactions
       and  logging).   For  a  general  description  of  the  DB
       package, see db_intro(3).

       This manual page describes the  specific  details  of  the
       locking   interface.    The   DbLock   class  is  used  in
       conjunction with DbLockTab(3) to  provide  general-purpose
       locking.   While  designed  to  work  with  the  other  Db
       classes, these classes are also useful  for  more  general
       locking  purposes.  Locks can be shared between processes.
       In most cases, when  multiple  threads  or  processes  are
       using  locking,  the  deadlock  detector,  db_deadlock(1),
       should be run.

  DbLock::put
       The DbLock::put  method  is  a  simple  interface  to  the
       DbLockTab::vec functionality, and is equivalent to calling
       the DbLockTab::vec  method  with  a  single  element  list
       array,  for which the op field is DB_LOCK_PUT and the lock
       field  is  represented  by   the   DbLock   object.    The
       DbLock::put   method   returns   success  and  failure  as
       described for the DbLockTab::vec method.

  DbLock::get_lock_id
       The  DbLock::get_lock_id  method   gets   the   underlying
       representation of the lock id.  Direct manipulation of the
       underlying representation is not recommended.

  DbLock::set_lock_id
       The  DbLock::set_lock_id  method   sets   the   underlying
       representation of the lock id.  Direct manipulation of the
       underlying representation  is  not  recommended.   Rather,
       DbLockTab::get  should  be  used  to initialize locks (see
       DbLockTab(3)), and the  copy  constructor  and  assignment
       operators can be used to assign to other DbLock objects.

ERRORS

       Methods  marked as returning errno will, by default, throw
       an exception that encapsulates the error information.  The
       default error behavior can be changed, see DbException(3).

       The DbLock::put method may fail and throw a DbException(3)

       or  return  errno  for any of the errors specified for the
       following DB and library functions: DbLock::detect(3),
       fcntl(2), fflush(3), lseek(2), memcpy(3), memset(3),
       mmap(2), munmap(2), strerror(3), and write(2).

       In addition, the DbLock::put method may fail and  throw  a
       DbException(3)   or   return   errno   for  the  following
       conditions:

       [EACCES]
            An attempt was made to release lock held  by  another
            locker.

       [EINVAL]
            An invalid flag value or parameter was specified.

BUGS

       If  a process dies while holding locks, those locks remain
       held and are never released.  In this case, all  processes
       should exit as quickly as possible, so that db_recover can
       be run.

SEE ALSO

       db_archive(1), db_checkpoint(1), db_deadlock(1), db_dump(1),
       db_load(1), db_recover(1), db_stat(1), db_intro(3),
       db_internal(3), db_thread(3), Db(3), Dbc(3), DbEnv(3),
       DbException(3), DbInfo(3), DbLock(3), DbLockTab(3), DbLog(3),
       DbLsn(3), DbMpool(3), DbMpoolFile(3), Dbt(3), DbTxn(3),
       DbTxnMgr(3)