Add doc file for pg_resetxlog.

doc/src/sgml/ref/pg_resetxlog.sgml

+<!--
+$Header: /cvsroot/pgsql/doc/src/sgml/ref/pg_resetxlog.sgml,v 1.1 2002/08/17 02:45:29 momjian Exp $
+PostgreSQL documentation
+-->
+
+<refentry id="APP-PGRESETXLOG">
+ <refmeta>
+  <refentrytitle id="APP-PGRESETXLOG-TITLE"><application>pg_resetxlog</application></refentrytitle>
+  <manvolnum>1</manvolnum>
+  <refmiscinfo>Application</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>pg_resetxlog</refname>
+  <refpurpose>reset write-ahead log file and optionally the pg_controldata file</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+  <cmdsynopsis>
+   <command>pg_resetxlog</command>
+   <arg><replaceable choice="plain">datadir</replaceable></arg>
+  </cmdsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1 id="R1-APP-PGRESETXLOG-1">
+  <title>Description</title>
+  <para>
+   <command>pg_resetxlog</command> clears the write-ahead log file and
+   optionally the <filename>pg_controldata</> file.  This is
+   used so the server can be started after these files have become corrupted.
+   (In every reported case, such file corruption has been caused 
+   by faulty hardware.)  It is to be used only as a last resort,
+   when the server will not start due to such corruption.
+  </para>
+
+  <para>
+   After running this command, the server may contain index corruption and
+   partially-committed transactions.  You should immediately dump your data
+   and reload.  After reload, check for partially committed transactions 
+   that may have been open at the time of the server crash.
+  </para>
+
+  <para>
+   <command>pg_resetxlog</command> can also fix a corrupted
+   <filename>pg_controldata</> file using the <literal>-f</>
+   flag.  Use this option when <command>pg_resetxlog</> reports it can't
+   reconstruct valid data for pg_control.
+  </para>
+
+  <para>
+   <command>pg_resetxlog</command> has a few more options for
+   special purposes.  Run the command with no arguments to see them.
+  </para>
+
+  <para>
+   This utility can only be run by the user who installed the server because
+   it requires read/write access to the <literal>datadir</>.
+   For safety reasons, you must specify the data directory on the command line. 
+   It does not use the environment variable <envar>PGDATA</>.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Notes</title>
+
+  <para>
+   This command can not be used when the <application>postmaster</> is 
+   running.
+  </para>
+ </refsect1>
+
+</refentry>
+
+<!-- Keep this comment at the end of the file
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+-->