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NAME

       relup - Release upgrade file

DESCRIPTION

       The  release  upgrade  file  describes  how  a release is upgraded in a
       running system.

       This file is automatically generated by systools:make_relup/3, 4, using
       a  release  resource file (.rel), application resource files (.app) and
       application upgrade files (.appup) as input.

FILE SYNTAX

       In a target system, the release upgrade file should be located  in  the
       OTP_ROOT/erts-EVsn/Vsn directory.

       The  relup  file  contains  one  single  Erlang term, which defines the
       instructions used to upgrade the release. The file  has  the  following
       syntax:

       {Vsn,
         [{UpFromVsn, Descr, Instructions}, ...],
         [{DownToVsn, Descr, Instructions}, ...]}.

         * Vsn = string() is the current version of the release.

         * UpFromVsn  =  string()  is  an  earlier  version  of the release to
           upgrade from.

         * Descr =  term()  is  a  user  defined  parameter  passed  from  the
           systools:make_relup/3,  4  function.  It will be used in the return
           value of release_handler:install_release/1, 2.

         * Instructions is a list of low-level release  upgrade  instructions,
           see appup(4).

           It consists of the release upgrade instructions from the respective
           application upgrade files (high-level instructions  are  translated
           to  low-level  instructions),  in  the  same  order as in the start
           script.

         * DownToVsn = string() is  an  earlier  version  of  the  release  to
           downgrade to.

       When  upgrading  from UpFromVsn with release_handler:install_release/1,
       2, there does not have to be an exact match of versions, but  UpFromVsn
       can be a sub-string of the current release version.

SEE ALSO

       app(4), appup(4), rel(4), release_handler(3erl), systools(3erl)