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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>14.5. Non-Durable Settings</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="populate.html" title="14.4. Populating a Database" /><link rel="next" href="parallel-query.html" title="Chapter 15. Parallel Query" /></head><body><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">14.5. Non-Durable Settings</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="populate.html" title="14.4. Populating a Database">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="performance-tips.html" title="Chapter 14. Performance Tips">Up</a></td><th width="60%" align="center">Chapter 14. Performance Tips</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 11.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="parallel-query.html" title="Chapter 15. Parallel Query">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="NON-DURABILITY"><div class="titlepage"><div><div><h2 class="title" style="clear: both">14.5. Non-Durable Settings</h2></div></div></div><a id="id-1.5.13.8.2" class="indexterm"></a><p>
Durability is a database feature that guarantees the recording of
committed transactions even if the server crashes or loses
power. However, durability adds significant database overhead,
so if your site does not require such a guarantee,
<span class="productname">PostgreSQL</span> can be configured to run
much faster. The following are configuration changes you can make
to improve performance in such cases. Except as noted below, durability
is still guaranteed in case of a crash of the database software;
only abrupt operating system stoppage creates a risk of data loss
or corruption when these settings are used.
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
Place the database cluster's data directory in a memory-backed
file system (i.e. <acronym class="acronym">RAM</acronym> disk). This eliminates all
database disk I/O, but limits data storage to the amount of
available memory (and perhaps swap).
</p></li><li class="listitem"><p>
Turn off <a class="xref" href="runtime-config-wal.html#GUC-FSYNC">fsync</a>; there is no need to flush
data to disk.
</p></li><li class="listitem"><p>
Turn off <a class="xref" href="runtime-config-wal.html#GUC-SYNCHRONOUS-COMMIT">synchronous_commit</a>; there might be no
need to force <acronym class="acronym">WAL</acronym> writes to disk on every
commit. This setting does risk transaction loss (though not data
corruption) in case of a crash of the <span class="emphasis"><em>database</em></span>.
</p></li><li class="listitem"><p>
Turn off <a class="xref" href="runtime-config-wal.html#GUC-FULL-PAGE-WRITES">full_page_writes</a>; there is no need
to guard against partial page writes.
</p></li><li class="listitem"><p>
Increase <a class="xref" href="runtime-config-wal.html#GUC-MAX-WAL-SIZE">max_wal_size</a> and <a class="xref" href="runtime-config-wal.html#GUC-CHECKPOINT-TIMEOUT">checkpoint_timeout</a>; this reduces the frequency
of checkpoints, but increases the storage requirements of
<code class="filename">/pg_wal</code>.
</p></li><li class="listitem"><p>
Create <a class="link" href="sql-createtable.html#SQL-CREATETABLE-UNLOGGED">unlogged
tables</a> to avoid <acronym class="acronym">WAL</acronym> writes, though it
makes the tables non-crash-safe.
</p></li></ul></div><p>
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