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| <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>pg_resetwal</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="app-pg-ctl.html" title="pg_ctl" /><link rel="next" href="app-pgrewind.html" title="pg_rewind" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center"><span class="application">pg_resetwal</span></th></tr><tr><td width="10%" align="left"><a accesskey="p" href="app-pg-ctl.html" title="pg_ctl">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="reference-server.html" title="PostgreSQL Server Applications">Up</a></td><th width="60%" align="center">PostgreSQL Server Applications</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 16.3 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="app-pgrewind.html" title="pg_rewind">Next</a></td></tr></table><hr /></div><div class="refentry" id="APP-PGRESETWAL"><div class="titlepage"></div><a id="id-1.9.5.8.1" class="indexterm"></a><div class="refnamediv"><h2><span class="refentrytitle"><span class="application">pg_resetwal</span></span></h2><p>pg_resetwal — reset the write-ahead log and other control information of a <span class="productname">PostgreSQL</span> database cluster</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p id="id-1.9.5.8.4.1"><code class="command">pg_resetwal</code> [ <code class="option">-f</code> | <code class="option">--force</code> ] [ <code class="option">-n</code> | <code class="option">--dry-run</code> ] [<em class="replaceable"><code>option</code></em>...] [ <code class="option">-D</code> | <code class="option">--pgdata</code> ]<em class="replaceable"><code>datadir</code></em> </p></div></div><div class="refsect1" id="R1-APP-PGRESETWAL-1"><h2>Description</h2><p> |
| <code class="command">pg_resetwal</code> clears the write-ahead log (WAL) and |
| optionally resets some other control information stored in the |
| <code class="filename">pg_control</code> file. This function is sometimes needed |
| if these files have become corrupted. It should be used only as a |
| last resort, when the server will not start due to such corruption. |
| </p><p> |
| After running this command, it should be possible to start the server, |
| but bear in mind that the database might contain inconsistent data due to |
| partially-committed transactions. You should immediately dump your data, |
| run <code class="command">initdb</code>, and restore. After restore, check for |
| inconsistencies and repair as needed. |
| </p><p> |
| This utility can only be run by the user who installed the server, because |
| it requires read/write access to the data directory. |
| For safety reasons, you must specify the data directory on the command line. |
| <code class="command">pg_resetwal</code> does not use the environment variable |
| <code class="envar">PGDATA</code>. |
| </p><p> |
| If <code class="command">pg_resetwal</code> complains that it cannot determine |
| valid data for <code class="filename">pg_control</code>, you can force it to proceed anyway |
| by specifying the <code class="option">-f</code> (force) option. In this case plausible |
| values will be substituted for the missing data. Most of the fields can be |
| expected to match, but manual assistance might be needed for the next OID, |
| next transaction ID and epoch, next multitransaction ID and offset, and |
| WAL starting location fields. These fields can be set using the options |
| discussed below. If you are not able to determine correct values for all |
| these fields, <code class="option">-f</code> can still be used, but |
| the recovered database must be treated with even more suspicion than |
| usual: an immediate dump and restore is imperative. <span class="emphasis"><em>Do not</em></span> |
| execute any data-modifying operations in the database before you dump, |
| as any such action is likely to make the corruption worse. |
| </p></div><div class="refsect1" id="id-1.9.5.8.6"><h2>Options</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">-f</code><br /></span><span class="term"><code class="option">--force</code></span></dt><dd><p> |
| Force <code class="command">pg_resetwal</code> to proceed even if it cannot determine |
| valid data for <code class="filename">pg_control</code>, as explained above. |
| </p></dd><dt><span class="term"><code class="option">-n</code><br /></span><span class="term"><code class="option">--dry-run</code></span></dt><dd><p> |
| The <code class="option">-n</code>/<code class="option">--dry-run</code> option instructs |
| <code class="command">pg_resetwal</code> to print the values reconstructed from |
| <code class="filename">pg_control</code> 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 <code class="command">pg_resetwal</code> |
| to proceed for real. |
| </p></dd><dt><span class="term"><code class="option">-V</code><br /></span><span class="term"><code class="option">--version</code></span></dt><dd><p>Display version information, then exit.</p></dd><dt><span class="term"><code class="option">-?</code><br /></span><span class="term"><code class="option">--help</code></span></dt><dd><p>Show help, then exit.</p></dd></dl></div><p> |
| The following options are only needed when |
| <code class="command">pg_resetwal</code> is unable to determine appropriate values |
| by reading <code class="filename">pg_control</code>. Safe values can be determined as |
| described below. For values that take numeric arguments, hexadecimal |
| values can be specified by using the prefix <code class="literal">0x</code>. |
| </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">-c <em class="replaceable"><code>xid</code></em>,<em class="replaceable"><code>xid</code></em></code><br /></span><span class="term"><code class="option">--commit-timestamp-ids=<em class="replaceable"><code>xid</code></em>,<em class="replaceable"><code>xid</code></em></code></span></dt><dd><p> |
| Manually set the oldest and newest transaction IDs for which the commit |
| time can be retrieved. |
| </p><p> |
| A safe value for the oldest transaction ID for which the commit time can |
| be retrieved (first part) can be determined by looking |
| for the numerically smallest file name in the directory |
| <code class="filename">pg_commit_ts</code> under the data directory. Conversely, a safe |
| value for the newest transaction ID for which the commit time can be |
| retrieved (second part) can be determined by looking for the numerically |
| greatest file name in the same directory. The file names are in |
| hexadecimal. |
| </p></dd><dt><span class="term"><code class="option">-e <em class="replaceable"><code>xid_epoch</code></em></code><br /></span><span class="term"><code class="option">--epoch=<em class="replaceable"><code>xid_epoch</code></em></code></span></dt><dd><p> |
| Manually set the next transaction ID's epoch. |
| </p><p> |
| The transaction ID epoch is not actually stored anywhere in the database |
| except in the field that is set by <code class="command">pg_resetwal</code>, |
| 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 <span class="application">Slony-I</span> and |
| <span class="application">Skytools</span> work correctly — |
| if so, an appropriate value should be obtainable from the state of |
| the downstream replicated database. |
| </p></dd><dt><span class="term"><code class="option">-l <em class="replaceable"><code>walfile</code></em></code><br /></span><span class="term"><code class="option">--next-wal-file=<em class="replaceable"><code>walfile</code></em></code></span></dt><dd><p> |
| Manually set the WAL starting location by specifying the name of the |
| next WAL segment file. |
| </p><p> |
| The name of next WAL segment file should be |
| larger than any WAL segment file name currently existing in |
| the directory <code class="filename">pg_wal</code> under the data directory. |
| These names are also in hexadecimal and have three parts. The first |
| part is the <span class="quote">“<span class="quote">timeline ID</span>”</span> and should usually be kept the same. |
| For example, if <code class="filename">00000001000000320000004A</code> is the |
| largest entry in <code class="filename">pg_wal</code>, use <code class="literal">-l 00000001000000320000004B</code> or higher. |
| </p><p> |
| Note that when using nondefault WAL segment sizes, the numbers in the WAL |
| file names are different from the LSNs that are reported by system |
| functions and system views. This option takes a WAL file name, not an |
| LSN. |
| </p><div class="note"><h3 class="title">Note</h3><p> |
| <code class="command">pg_resetwal</code> itself looks at the files in |
| <code class="filename">pg_wal</code> and chooses a default <code class="option">-l</code> setting |
| beyond the last existing file name. Therefore, manual adjustment of |
| <code class="option">-l</code> should only be needed if you are aware of WAL segment |
| files that are not currently present in <code class="filename">pg_wal</code>, such as |
| entries in an offline archive; or if the contents of |
| <code class="filename">pg_wal</code> have been lost entirely. |
| </p></div></dd><dt><span class="term"><code class="option">-m <em class="replaceable"><code>mxid</code></em>,<em class="replaceable"><code>mxid</code></em></code><br /></span><span class="term"><code class="option">--multixact-ids=<em class="replaceable"><code>mxid</code></em>,<em class="replaceable"><code>mxid</code></em></code></span></dt><dd><p> |
| Manually set the next and oldest multitransaction ID. |
| </p><p> |
| A safe value for the next multitransaction ID (first part) can be |
| determined by looking for the numerically largest file name in the |
| directory <code class="filename">pg_multixact/offsets</code> under the data directory, |
| adding one, and then multiplying by 65536 (0x10000). Conversely, a safe |
| value for the oldest multitransaction ID (second part of |
| <code class="option">-m</code>) 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. |
| </p></dd><dt><span class="term"><code class="option">-o <em class="replaceable"><code>oid</code></em></code><br /></span><span class="term"><code class="option">--next-oid=<em class="replaceable"><code>oid</code></em></code></span></dt><dd><p> |
| Manually set the next OID. |
| </p><p> |
| 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. |
| </p></dd><dt><span class="term"><code class="option">-O <em class="replaceable"><code>mxoff</code></em></code><br /></span><span class="term"><code class="option">--multixact-offset=<em class="replaceable"><code>mxoff</code></em></code></span></dt><dd><p> |
| Manually set the next multitransaction offset. |
| </p><p> |
| A safe value can be determined by looking for the numerically largest |
| file name in the directory <code class="filename">pg_multixact/members</code> 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. |
| </p></dd><dt><span class="term"><code class="option">--wal-segsize=<em class="replaceable"><code>wal_segment_size</code></em></code></span></dt><dd><p> |
| Set the new WAL segment size, in megabytes. The value must be set to a |
| power of 2 between 1 and 1024 (megabytes). See the same option of <a class="xref" href="app-initdb.html" title="initdb"><span class="refentrytitle"><span class="application">initdb</span></span></a> for more information. |
| </p><div class="note"><h3 class="title">Note</h3><p> |
| While <code class="command">pg_resetwal</code> will set the WAL starting address |
| beyond the latest existing WAL segment file, some segment size changes |
| can cause previous WAL file names to be reused. It is recommended to |
| use <code class="option">-l</code> together with this option to manually set the |
| WAL starting address if WAL file name overlap will cause problems with |
| your archiving strategy. |
| </p></div></dd><dt><span class="term"><code class="option">-u <em class="replaceable"><code>xid</code></em></code><br /></span><span class="term"><code class="option">--oldest-transaction-id=<em class="replaceable"><code>xid</code></em></code></span></dt><dd><p> |
| Manually set the oldest unfrozen transaction ID. |
| </p><p> |
| A safe value can be determined by looking for the numerically smallest |
| file name in the directory <code class="filename">pg_xact</code> under the data directory |
| 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 <code class="filename">0007</code> is the smallest entry |
| in <code class="filename">pg_xact</code>, <code class="literal">-u 0x700000</code> will work (five |
| trailing zeroes provide the proper multiplier). |
| </p></dd><dt><span class="term"><code class="option">-x <em class="replaceable"><code>xid</code></em></code><br /></span><span class="term"><code class="option">--next-transaction-id=<em class="replaceable"><code>xid</code></em></code></span></dt><dd><p> |
| Manually set the next transaction ID. |
| </p><p> |
| A safe value can be determined by looking for the numerically largest |
| file name in the directory <code class="filename">pg_xact</code> 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 <code class="filename">0011</code> is the largest entry |
| in <code class="filename">pg_xact</code>, <code class="literal">-x 0x1200000</code> will work (five |
| trailing zeroes provide the proper multiplier). |
| </p></dd></dl></div></div><div class="refsect1" id="id-1.9.5.8.7"><h2>Environment</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="envar">PG_COLOR</code></span></dt><dd><p> |
| Specifies whether to use color in diagnostic messages. Possible values |
| are <code class="literal">always</code>, <code class="literal">auto</code> and |
| <code class="literal">never</code>. |
| </p></dd></dl></div></div><div class="refsect1" id="id-1.9.5.8.8"><h2>Notes</h2><p> |
| This command must not be used when the server is |
| running. <code class="command">pg_resetwal</code> will refuse to start up if |
| it finds a server lock file in the data directory. If the |
| server crashed then a lock file might have been left |
| behind; in that case you can remove the lock file to allow |
| <code class="command">pg_resetwal</code> to run. But before you do |
| so, make doubly certain that there is no server process still alive. |
| </p><p> |
| <code class="command">pg_resetwal</code> works only with servers of the same |
| major version. |
| </p></div><div class="refsect1" id="id-1.9.5.8.9"><h2>See Also</h2><span class="simplelist"><a class="xref" href="app-pgcontroldata.html" title="pg_controldata"><span class="refentrytitle"><span class="application">pg_controldata</span></span></a></span></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="app-pg-ctl.html" title="pg_ctl">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="reference-server.html" title="PostgreSQL Server Applications">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="app-pgrewind.html" title="pg_rewind">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><span class="application">pg_ctl</span> </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 16.3 Documentation">Home</a></td><td width="40%" align="right" valign="top"> <span class="application">pg_rewind</span></td></tr></table></div></body></html> |
