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Update pg_resetxlog's documentation on multixacts

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I added some more functionality to it in 0ac5ad5134 but neglected to
add it to the docs.

Per Peter Eisentraut in message
1367112171.32604.4.camel@vanquo.pezone.net
This commit is contained in:
Alvaro Herrera
2013-06-27 15:31:04 -04:00
parent deac50021b
commit 5e1ed63ac2
2 changed files with 14 additions and 10 deletions
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22
doc/src/sgml/ref/pg_resetxlog.sgml
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@ -27,7 +27,7 @@ PostgreSQL documentation
<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></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 choice="plain"><replaceable>datadir</replaceable></arg>
@ -81,7 +81,7 @@ PostgreSQL documentation
<option>-m</>, <option>-O</>,
and <option>-l</>
options allow the next OID, next transaction ID, next transaction ID's
epoch, next multitransaction ID, next multitransaction offset, and WAL
epoch, next and oldest multitransaction ID, next multitransaction offset, 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
@ -104,12 +104,16 @@ PostgreSQL documentation
<listitem>
<para>
A safe value for the next multitransaction ID (<option>-m</>)
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. As above,
the file names are in hexadecimal, so the easiest way to do this is to
specify the option value in hexadecimal and add four zeroes.
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.
</para>
</listitem>
@ -118,9 +122,9 @@ PostgreSQL documentation
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 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 add four zeroes.
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.
</para>
</listitem>