path: root/lib/mnesia/doc/src/mnesia_registry.xml

<?xml version="1.0" encoding="latin1" ?>
<!DOCTYPE erlref SYSTEM "erlref.dtd">

<erlref>
  <header>
    <copyright>
      <year>1998</year>
      <year>2007</year>
      <holder>Ericsson AB, All Rights Reserved</holder>
    </copyright>
    <legalnotice>
  The contents of this file are subject to the Erlang Public License,
  Version 1.1, (the "License"); you may not use this file except in
  compliance with the License. You should have received a copy of the
  Erlang Public License along with this software. If not, it can be
  retrieved online at http://www.erlang.org/.

  Software distributed under the License is distributed on an "AS IS"
  basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
  the License for the specific language governing rights and limitations
  under the License.

  The Initial Developer of the Original Code is Ericsson AB.
    </legalnotice>

    <title>mnesia_registry</title>
    <prepared>Dan Gudmundsson and H&aring;kan Mattsson</prepared>
    <responsible></responsible>
    <docno></docno>
    <approved></approved>
    <checked></checked>
    <date>98-04-24</date>
    <rev>A</rev>
    <file>mnesia_registry.sgml</file>
  </header>
  <module>mnesia_registry</module>
  <modulesummary>Dump support for registries in erl_interface. </modulesummary>
  <description>
    <p>The module <c>mnesia_registry</c> is usually  part of
      <c>erl_interface</c>, but for the time being, it is a part of the
      Mnesia application.
      </p>
    <p><c>mnesia_registry</c> is mainly an module intended for
      internal usage within OTP, but it has two functions that
      are exported for public use.
      </p>
    <p>On C-nodes <c>erl_interface</c> has support for registry
      tables. These reside in RAM on the C-node but they may also be
      dumped into Mnesia tables. By default, the dumping of registry
      tables via <c>erl_interface</c> causes a corresponding Mnesia
      table to be created with <c>mnesia_registry:create_table/1</c>
      if necessary.
      </p>
    <p>The tables that are created with these functions can be
      administered as all other Mnesia tables. They may be included in
      backups or replicas may be added etc. The tables are in fact
      normal Mnesia tables owned by the user of the corresponding
      <c>erl_interface</c> registries.
      </p>
  </description>
  <funcs>
    <func>
      <name>create_table(Tab) -> ok | exit(Reason)</name>
      <fsummary>Creates a registry table in Mnesia.</fsummary>
      <desc>
        <p>This is a wrapper function for
          <c>mnesia:create_table/2</c> which creates a table (if there is no existing table)
          with an appropriate set of <c>attributes</c>. The table will
          only reside on the local node and its storage type will be
          the same as the <c>schema</c> table on the local
          node, ie. <c>{ram_copies,[node()]}</c> or
          <c>{disc_copies,[node()]}</c>.
          </p>
        <p>It is this function that is used by <c>erl_interface</c> to
          create the Mnesia table if it did not already exist.</p>
      </desc>
    </func>
    <func>
      <name>create_table(Tab, TabDef) -> ok | exit(Reason)</name>
      <fsummary>Creates a customized registry table in Mnesia. </fsummary>
      <desc>
        <p>This is a wrapper function for
          <c>mnesia:create_table/2</c> which creates a table (if there is no existing table)
          with an appropriate set of <c>attributes</c>. The attributes
          and <c>TabDef</c> are forwarded to
          <c>mnesia:create_table/2</c>.  For example, if the table should
          reside as <c>disc_only_copies</c> on all nodes a call would
          look like:</p>
        <code type="none">
          TabDef = [{{disc_only_copies, node()|nodes()]}],
          mnesia_registry:create_table(my_reg, TabDef)
        </code>
      </desc>
    </func>
  </funcs>

  <section>
    <title>See Also</title>
    <p>mnesia(3), erl_interface(3)
      </p>
  </section>
  
</erlref>