The XLOCK.SBR routine normally returns the job number of the job which is in possession of a lock in the MODE parameter, if an attempt is made to create a conflicting lock. Under AMOS, if an attempt is made to duplicate a lock which your job already owns, then a MODE of zero is returned, indicating success, even though no extra lock information is created. This, although contrary to the standard documentation, is the default operation under A-Shell. If the MXLOCK code is specified, then the operation of XLOCK conforms exactly to the standard documentation. An attempt to create a lock which conflicts only with a lock possessed by your own job, will still return a non-zero MODE, the job number of your own job.