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<chapter>
  <header>
    <copyright>
      <year>2004</year><year>2016</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
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      Licensed under the Apache License, Version 2.0 (the "License");
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    <title>Mnesia Release Notes</title>
    <prepared>Dan Gudmundsson and H&aring;kan Mattsson</prepared>
    <responsible></responsible>
    <docno></docno>
    <approved></approved>
    <checked></checked>
    <date>04-08-22</date>
    <rev>AE</rev>
    <file>notes_history.sgml</file>
  </header>
  <p>This document describes the changes made to the Mnesia system
    from version to version.  The intention of this document is to
    list all incompatibilities as well as all enhancements and
    bugfixes for every release of Mnesia. Each release of Mnesia
    thus constitutes one section in this document. The title of each
    section is the version number of Mnesia.</p>

  <section><title>Mnesia 4.3.7</title>
    <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
            Removed a memory leak on ram-only nodes, introduced in
            <c>mnesia-4.3.6</c>.</p>
          <p>
            Own Id: OTP-6936 Aux Id: seq10786 </p>
        </item>
      </list>
    </section>
    <section>
      <title>Known Bugs and Problems</title>
      <list type="bulleted">
        <item>
          <p>Rearranging fragmented tables is an O(N^2)
            operation.</p>
          <p>Own Id: OTP-6300</p>
        </item>
      </list>
    </section>
    
  </section>
  

  <section>
    <title>Mnesia 4.3.6</title>

      <section><title>Fixed Bugs and Malfunctions</title>
      <list>
        <item>
          <p>
            A bug causing lots of records to be lost at startup from
            an installed fallback has been fixed. The bug did however
            not show up when a backup file generated with
            <c>mnesia:backup/1</c> or
            <c>mnesia:backup_checkpoint/2</c> was installed as
            fallback. In order to trigger the bug, the items in the
            backup file had to be rearranged in such an order that
            records from different tables were interleaved with each
            other.</p>
          <p>
            Own Id: OTP-6903 Aux Id: seq10763 </p>
        </item>
        <item>
          <p>
            Mnesia sometimes failed to commit schema operations on
            all nodes, this have been seen on smp machines but could
            happen on single processor as well with some bad timing.</p>
          <p>
            Own Id: OTP-6904</p>
        </item>
        <item>
          <p>
            <c>mnesia:select/1</c> failed to return all matches on
            remote nodes if something was written to the table
            earlier in the same transaction.</p>
          <p>
            Own Id: OTP-6908</p>
        </item>
      </list>
    </section>

    <section>
      <title>Known Bugs and Problems</title>
      <list type="bulleted">
        <item>
          <p>Rearranging fragmented tables is an O(N^2)
            operation.</p>
          <p>Own Id: OTP-6300</p>
        </item>
      </list>
    </section>
  </section>

  <section>
    <title>Mnesia 4.3.5</title>

    <section>
      <title>Fixed Bugs and Malfunctions</title>
      <list type="bulleted">
        <item>
          <p>The internal index tables on bag tables where not always
            cleaned correctly. Thanks Christopher Faulet and Salazard
            Remy.</p>
          <p>Own Id: OTP-6587</p>
        </item>
        <item>
          <p>Changing the copy type with
            <c>mnesia:change_table_copy/3</c> on a node which was down
            was not handled correctly, that caused an eternal table
            lock on the alive nodes. Thanks Hal Snyder.</p>
          <p>Own
            Id: OTP-6709</p>
        </item>
      </list>
    </section>

    <section>
      <title>Known Bugs and Problems</title>
      <list type="bulleted">
        <item>
          <p>Rearranging fragmented tables is an O(N^2)
            operation.</p>
          <p>Own Id: OTP-6300</p>
        </item>
      </list>
    </section>
  </section>

  <section>
    <title>Mnesia 4.3.4</title>

    <section>
      <title>Fixed Bugs and Malfunctions</title>
      <list type="bulleted">
        <item>
          <p>Adding fragments to ram_copies tables was allowed on
            nodes that where down.</p>
          <p>Own Id: OTP-6367</p>
        </item>
        <item>
          <p>Mnesia leaked transaction decisions (memory and disk
            space).</p>
          <p>Own Id: OTP-6464</p>
        </item>
        <item>
          <p><c>dirty_update_counter/3</c> did not work properly on
            disc tables when the counter was not initiated (Thanks to
            Sebastien Saint-Sevin).</p>
          <p>Own Id: OTP-6545</p>
        </item>
        <item>
          <p>Chunked <c>mnesia:select</c> on fragmented tables could
            crash (Thanks to Primanathan Reddy).</p>
          <p>Own Id:
            OTP-6548</p>
        </item>
      </list>
    </section>

    <section>
      <title>Improvements and New Features</title>
      <list type="bulleted">
        <item>
          <p>Introduced a new configure parameter dc_dump_limit.</p>
          <p>Removed dead code (dialyzer warnings) and debugging
            features that called interpreter commands.</p>
          <p>Minor
            performance increase when a lot of simultaneous
            transactions where active. </p>
          <p>Thank you Scott Lystig
            Fritchie for debugging and bug reports.</p>
          <p>Own Id:
            OTP-6478</p>
        </item>
      </list>
    </section>

    <section>
      <title>Known Bugs and Problems</title>
      <list type="bulleted">
        <item>
          <p>Rearranging fragmented tables is an O(N^2)
            operation.</p>
          <p>Own Id: OTP-6300</p>
        </item>
      </list>
    </section>
  </section>

  <section>
    <title>Mnesia 4.3.3</title>

    <section>
      <title>Fixed Bugs and Malfunctions</title>
      <list type="bulleted">
        <item>
          <p>Mnesia could crash during startup when loading tables
            from remote node. </p>
          <p>Own Id: OTP-6298 Aux Id: seq10402 </p>
        </item>
        <item>
          <p>Mnesia could fail to update all copies during
            del_table_copy. </p>
          <p>Own Id: OTP-6299</p>
        </item>
      </list>
    </section>

    <section>
      <title>Known Bugs and Problems</title>
      <list type="bulleted">
        <item>
          <p>Rearranging fragmented tables is an O(N^2) operation.</p>
          <p>Own Id: OTP-6300</p>
        </item>
      </list>
    </section>
  </section>

  <section>
    <title>Mnesia 4.3.2</title>

    <section>
      <title>Fixed Bugs and Malfunctions</title>
      <list type="bulleted">
        <item>
          <p>Mnesia sometimes failed to remove [d]ets table fixation,
            when using <c>mnesia:first/1</c>,<c>mnesia:next/2</c> or
            <c>qlc</c> this could cause that deleted records are not
            actually deleted in the [d]ets table and that
            <c>mnesia:[dirty_]first/1</c> reported the wrong key. </p>
          <p>Own Id: OTP-6193 Aux Id: seq10376</p>
        </item>
      </list>
    </section>
  </section>

  <section>
    <title>Mnesia 4.3.1</title>

    <section>
      <title>Fixed Bugs and Malfunctions</title>
      <list type="bulleted">
        <item>
          <p>Mnesia could crash (bad match in mnesia_controller)
            during start. </p>
          <p>Own Id: OTP-6116 Aux Id: seq10305 </p>
        </item>
      </list>
    </section>
  </section>

  <section>
    <title>Mnesia 4.3</title>

    <section>
      <title>Fixed Bugs and Malfunctions</title>
      <list type="bulleted">
        <item>
          <p>Deleting tables during the start of mnesia on another
            node caused problems. </p>
          <p>Own Id: OTP-5928 Aux Id:
            seq10111 </p>
        </item>
        <item>
          <p>Killing processes that runs nested transactions could
            crash mnesia. </p>
          <p>Own Id: OTP-6027 Aux Id: seq10244 </p>
        </item>
        <item>
          <p>Creating or deleting tables with a checkpoint activated
            could crash mnesia </p>
          <p>Own Id: OTP-6064</p>
        </item>
        <item>
          <p>Table loading could be mixed with schema operations
            which could cause troubles. </p>
          <p>Own Id: OTP-6065 Aux Id:
            seq10291 </p>
        </item>
      </list>
    </section>

    <section>
      <title>Improvements and New Features</title>
      <list type="bulleted">
        <item>
          <p>Added parallel table loaders to increase startup
            performance when the system have many small tables. The
            configuration variable <c>no_table_loaders</c> configures
            the number of loaders, default is two. </p>
          <p>Own Id:
            OTP-6087</p>
        </item>
      </list>
    </section>
  </section>
</chapter>

