LOCK V1.0 Technical Release Notes




             All information necessary to use LOCK is available  in  the
        help text.  This file describes aspects of the implementation.


             LOCK is installed using the VMSINSTAL procedure.  Treat  it
        in  a  manner  similar  to  Digital layered products you install
        using VMSINSTAL.  However, since LOCK is not a Digital  product,
        it  does not automatically get put in the same places as Digital
        installations.

             During the installation, you will be asked whether  or  not
        you wish to install LOCK as though it came from Digital.  If you
        answer in the affirmative, LOCK will be  added  to  the  default
        command tables, help library, and SYS$SYSTEM.  If you answer 'N'
        to the question, you will be asked for each storage area as  the
        installation  procedure  comes  to it.  The defaults will be the
        Digital  areas  (i.e.,  SYS$SYSTEM,  SYS$HELP:HELPLIB.HLB,   and
        SYS$SHARE:DCLTABLES.EXE),  but  you may override them and supply
        your site-specific locations.  Note that the command  table  and
        help  library  must  already  exist  - the installation will NOT
        create them if they aren't already there.

             The IVP should output a series  of  messages.   The  header
        text of these messages should look like this:

                    %LOCK-S-OBTAINED
                    %F-LOCKED
                    %I-LOCKED
                1   %S-OBTAINED
                1   %LOCK-S-CONVERTED
                2   %LOCK-S-RELEASED
                2   %S-RELEASED

             Those messages  marked  '1'  above  may  come  out  in  the
        opposite  order, as may those marked with a '2.' This is normal,
        and not cause for concern.   It  stems  from  a  race  condition
        between  the  master  and  slave processes trying to write their
        respective messages to the output stream.


             In order to work properly, LOCK must  either  be  installed
        with  CMKRNL  privilege  or all processes which will be using it
        must possess that privilege.  In addition, the same  holds  true
        for  the  SYSLCK  privilege if system-wide locks are to be used.
        Appropriate changes may need to be made  to  your  site-specific
        startup procedure(s).



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             LOCK  works  by  taking  out  locks  at  supervisor   mode.
        Continuity  is  maintained  by  storing the contents of the lock
        status  block  in  a  protected  logical  name.   LOCK  must  be
        installed  with  the CMKRNL privilege both because of the manner
        in which it protects this logical name  (process  table,  kernel
        mode,  NO_ALIAS  and  CONFINE  attributes  -  means  that only a
        program in kernel mode can change or delete it) and  because  it
        changes  to kernel mode to access resources with supervisor-mode
        locks.