Skip to content

P
Postgres FD Implementation
Commit e19e4cf0 authored by Peter Eisentraut's avatar Peter Eisentraut
Browse files
Options

doc: Reorganize pg_resetxlog reference page 

The pg_resetxlog reference page didn't have a proper options list, only
running text listing the options and some explanations of them.  This
might have worked when there were only a few options, but the list has
grown over the releases, and now it's hard to find an option and its
associated explanation.  So write out the options list as on other
reference pages.
parent 28f6df3c
Show whitespace changes
Inline Side-by-side
Showing with 144 additions and 78 deletions
doc/src/sgml/ref/pg_resetxlog.sgml
View file @ e19e4cf0
......@@ -22,15 +22,9 @@ PostgreSQL documentation
<refsynopsisdiv>
<cmdsynopsis>
<command>pg_resetxlog</command>
<arg choice="opt"><option>-c</option> <replaceable class="parameter">xid</replaceable>,<replaceable class="parameter">xid</replaceable></arg>
<arg choice="opt"><option>-f</option></arg>
<arg choice="opt"><option>-n</option></arg>
<arg choice="opt"><option>-o</option> <replaceable class="parameter">oid</replaceable></arg>
<arg choice="opt"><option>-x</option> <replaceable class="parameter">xid</replaceable></arg>
<arg choice="opt"><option>-e</option> <replaceable class="parameter">xid_epoch</replaceable></arg>
<arg choice="opt"><option>-m</option> <replaceable class="parameter">mxid</replaceable>,<replaceable class="parameter">mxid</replaceable></arg>
<arg choice="opt"><option>-O</option> <replaceable class="parameter">mxoff</replaceable></arg>
<arg choice="opt"><option>-l</option> <replaceable class="parameter">xlogfile</replaceable></arg>
<arg rep="repeat"><replaceable>option</replaceable></arg>
<arg choice="req"><arg choice="opt"><option>-D</option></arg> <replaceable class="parameter">datadir</replaceable></arg>
</cmdsynopsis>
</refsynopsisdiv>
......@@ -76,78 +70,108 @@ PostgreSQL documentation
execute any data-modifying operations in the database before you dump,
as any such action is likely to make the corruption worse.
</para>
</refsect1>
<para>
The <option>-o</>, <option>-x</>, <option>-e</>,
<option>-m</>, <option>-O</>,
<option>-c</>
and <option>-l</>
options allow the next OID, next transaction ID, next transaction ID's
epoch, next and oldest multitransaction ID, next multitransaction offset,
oldest and newest transaction IDs for which the commit time can be retrieved,
and WAL
starting address values to be set manually. These are only needed when
<command>pg_resetxlog</command> is unable to determine appropriate values
by reading <filename>pg_control</>. Safe values can be determined as
follows:
<refsect1>
<title>Options</title>
<itemizedlist>
<variablelist>
<varlistentry>
<term><option>-f</option></term>
<listitem>
<para>
A safe value for the next transaction ID (<option>-x</>)
can be determined by looking for the numerically largest
file name in the directory <filename>pg_clog</> under the data directory,
adding one,
and then multiplying by 1048576. Note that the file names are in
hexadecimal. It is usually easiest to specify the option value in
hexadecimal too. For example, if <filename>0011</> is the largest entry
in <filename>pg_clog</>, <literal>-x 0x1200000</> will work (five
trailing zeroes provide the proper multiplier).
Force <command>pg_resetxlog</command> to proceed even if it cannot determine
valid data for <filename>pg_control</>, as explained above.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-n</option></term>
<listitem>
<para>
A safe value for the next multitransaction ID (first part of <option>-m</>)
can be determined by looking for the numerically largest
file name in the directory <filename>pg_multixact/offsets</> under the
data directory, adding one, and then multiplying by 65536.
Conversely, a safe value for the oldest multitransaction ID (second part of
<option>-m</>)
can be determined by looking for the numerically smallest
file name in the same directory and multiplying by 65536.
As above, the file names are in hexadecimal, so the easiest way to do
this is to specify the option value in hexadecimal and append four zeroes.
The <option>-n</> (no operation) option instructs
<command>pg_resetxlog</command> to print the values reconstructed from
<filename>pg_control</> and values about to be changed, and then exit
without modifying anything. This is mainly a debugging tool, but can be
useful as a sanity check before allowing <command>pg_resetxlog</command>
to proceed for real.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-V</option></term>
<term><option>--version</option></term>
<listitem><para>Display version information, then exit.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>-?</option></term>
<term><option>--help</option></term>
<listitem><para>Show help, then exit.</para></listitem>
</varlistentry>
</variablelist>
<listitem>
<para>
A safe value for the next multitransaction offset (<option>-O</>)
can be determined by looking for the numerically largest
file name in the directory <filename>pg_multixact/members</> under the
data directory, adding one, and then multiplying by 52352. As above,
the file names are in hexadecimal. There is no simple recipe such as
the ones above of appending zeroes.
The following options are only needed when
<command>pg_resetxlog</command> is unable to determine appropriate values
by reading <filename>pg_control</>. Safe values can be determined as
described below. For values that take numeric arguments, hexadecimal
values can be specified by using the prefix <literal>0x</literal>.
</para>
</listitem>
<variablelist>
<varlistentry>
<term><option>-c</option> <replaceable class="parameter">xid</replaceable>,<replaceable class="parameter">xid</replaceable></term>
<listitem>
<para>
Manually set the oldest and newest transaction IDs for which the commit
time can be retrieved.
</para>
<para>
A safe value for the oldest transaction ID for which the commit time can
be retrieved (first part of <option>-c</>) can be determined by looking
be retrieved (first part) can be determined by looking
for the numerically smallest file name in the directory
<filename>pg_commit_ts</> under the data directory. Conversely, a safe
value for the newest transaction ID for which the commit time can be
retrieved (second part of <option>-c</>) can be determined by looking for
the numerically greatest file name in the same directory. As above, the
file names are in hexadecimal.
retrieved (second part) can be determined by looking for the numerically
greatest file name in the same directory. The file names are in
hexadecimal.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-e</option> <replaceable class="parameter">xid_epoch</replaceable></term>
<listitem>
<para>
Manually set the next transaction ID's epoch.
</para>
<para>
The transaction ID epoch is not actually stored anywhere in the database
except in the field that is set by <command>pg_resetxlog</command>,
so any value will work so far as the database itself is concerned.
You might need to adjust this value to ensure that replication
systems such as <application>Slony-I</> and
<application>Skytools</> work correctly &mdash;
if so, an appropriate value should be obtainable from the state of
the downstream replicated database.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-l</option> <replaceable class="parameter">xlogfile</replaceable></term>
<listitem>
<para>
The WAL starting address (<option>-l</>) should be
Manually set the WAL starting address.
</para>
<para>
The WAL starting address should be
larger than any WAL segment file name currently existing in
the directory <filename>pg_xlog</> under the data directory.
These names are also in hexadecimal and have three parts. The first
......@@ -168,46 +192,81 @@ PostgreSQL documentation
</para>
</note>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-m</option> <replaceable class="parameter">mxid</replaceable>,<replaceable class="parameter">mxid</replaceable></term>
<listitem>
<para>
Manually set the next and oldest multitransaction ID.
</para>
<para>
A safe value for the next multitransaction ID (first part) can be
determined by looking for the numerically largest file name in the
directory <filename>pg_multixact/offsets</> under the data directory,
adding one, and then multiplying by 65536 (0x10000). Conversely, a safe
value for the oldest multitransaction ID (second part of
<option>-m</>) can be determined by looking for the numerically smallest
file name in the same directory and multiplying by 65536. The file
names are in hexadecimal, so the easiest way to do this is to specify
the option value in hexadecimal and append four zeroes.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-o</option> <replaceable class="parameter">oid</replaceable></term>
<listitem>
<para>
Manually set the next OID.
</para>
<para>
There is no comparably easy way to determine a next OID that's beyond
the largest one in the database, but fortunately it is not critical to
get the next-OID setting right.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-O</option> <replaceable class="parameter">mxoff</replaceable></term>
<listitem>
<para>
The transaction ID epoch is not actually stored anywhere in the database
except in the field that is set by <command>pg_resetxlog</command>,
so any value will work so far as the database itself is concerned.
You might need to adjust this value to ensure that replication
systems such as <application>Slony-I</> and
<application>Skytools</> work correctly &mdash;
if so, an appropriate value should be obtainable from the state of
the downstream replicated database.
</para>
</listitem>
</itemizedlist>
Manually set the next multitransaction offset.
</para>
<para>
The <option>-n</> (no operation) option instructs
<command>pg_resetxlog</command> to print the values reconstructed from
<filename>pg_control</> and values about to be changed, and then exit
without modifying anything. This is mainly a debugging tool, but can be
useful as a sanity check before allowing <command>pg_resetxlog</command>
to proceed for real.
A safe value can be determined by looking for the numerically largest
file name in the directory <filename>pg_multixact/members</> under the
data directory, adding one, and then multiplying by 52352 (0xCC80).
The file names are in hexadecimal. There is no simple recipe such as
the ones for other options of appending zeroes.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-x</option> <replaceable class="parameter">xid</replaceable></term>
<listitem>
<para>
The <option>-V</> and <option>--version</> options print
the <application>pg_resetxlog</application> version and exit. The
options <option>-?</> and <option>--help</> show supported arguments,
and exit.
Manually set the next transaction ID.
</para>
<para>
A safe value can be determined by looking for the numerically largest
file name in the directory <filename>pg_clog</> under the data directory,
adding one,
and then multiplying by 1048576 (0x100000). Note that the file names are in
hexadecimal. It is usually easiest to specify the option value in
hexadecimal too. For example, if <filename>0011</> is the largest entry
in <filename>pg_clog</>, <literal>-x 0x1200000</> will work (five
trailing zeroes provide the proper multiplier).
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
......@@ -224,4 +283,11 @@ PostgreSQL documentation
</para>
</refsect1>
<refsect1>
<title>See Also</title>
<simplelist type="inline">
<member><xref linkend="app-pgcontroldata"></member>
</simplelist>
</refsect1>
</refentry>
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment