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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!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>20.14. Error Handling</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="runtime-config-compatible.html" title="20.13. Version and Platform Compatibility" /><link rel="next" href="runtime-config-preset.html" title="20.15. Preset Options" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">20.14. Error Handling</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="runtime-config-compatible.html" title="20.13. Version and Platform Compatibility">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="runtime-config.html" title="Chapter 20. Server Configuration">Up</a></td><th width="60%" align="center">Chapter 20. Server Configuration</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 15.6 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="runtime-config-preset.html" title="20.15. Preset Options">Next</a></td></tr></table><hr /></div><div class="sect1" id="RUNTIME-CONFIG-ERROR-HANDLING"><div class="titlepage"><div><div><h2 class="title" style="clear: both">20.14. Error Handling</h2></div></div></div><div class="variablelist"><dl class="variablelist"><dt id="GUC-EXIT-ON-ERROR"><span class="term"><code class="varname">exit_on_error</code> (<code class="type">boolean</code>)
      <a id="id-1.6.7.17.2.1.1.3" class="indexterm"></a>
      </span></dt><dd><p>
        If on, any error will terminate the current session.  By default,
        this is set to off, so that only FATAL errors will terminate the
        session.
       </p></dd><dt id="GUC-RESTART-AFTER-CRASH"><span class="term"><code class="varname">restart_after_crash</code> (<code class="type">boolean</code>)
      <a id="id-1.6.7.17.2.2.1.3" class="indexterm"></a>
      </span></dt><dd><p>
        When set to on, which is the default, <span class="productname">PostgreSQL</span>
        will automatically reinitialize after a backend crash.  Leaving this
        value set to on is normally the best way to maximize the availability
        of the database.  However, in some circumstances, such as when
        <span class="productname">PostgreSQL</span> is being invoked by clusterware, it may be
        useful to disable the restart so that the clusterware can gain
        control and take any actions it deems appropriate.
       </p><p>
        This parameter can only be set in the <code class="filename">postgresql.conf</code>
        file or on the server command line.
       </p></dd><dt id="GUC-DATA-SYNC-RETRY"><span class="term"><code class="varname">data_sync_retry</code> (<code class="type">boolean</code>)
      <a id="id-1.6.7.17.2.3.1.3" class="indexterm"></a>
      </span></dt><dd><p>
        When set to off, which is the default, <span class="productname">PostgreSQL</span>
        will raise a PANIC-level error on failure to flush modified data files
        to the file system.  This causes the database server to crash.  This
        parameter can only be set at server start.
       </p><p>
        On some operating systems, the status of data in the kernel's page
        cache is unknown after a write-back failure.  In some cases it might
        have been entirely forgotten, making it unsafe to retry; the second
        attempt may be reported as successful, when in fact the data has been
        lost.  In these circumstances, the only way to avoid data loss is to
        recover from the WAL after any failure is reported, preferably
        after investigating the root cause of the failure and replacing any
        faulty hardware.
       </p><p>
        If set to on, <span class="productname">PostgreSQL</span> will instead
        report an error but continue to run so that the data flushing
        operation can be retried in a later checkpoint.  Only set it to on
        after investigating the operating system's treatment of buffered data
        in case of write-back failure.
       </p></dd><dt id="GUC-RECOVERY-INIT-SYNC-METHOD"><span class="term"><code class="varname">recovery_init_sync_method</code> (<code class="type">enum</code>)
       <a id="id-1.6.7.17.2.4.1.3" class="indexterm"></a>
      </span></dt><dd><p>
        When set to <code class="literal">fsync</code>, which is the default,
        <span class="productname">PostgreSQL</span> will recursively open and
        synchronize all files in the data directory before crash recovery
        begins.  The search for files will follow symbolic links for the WAL
        directory and each configured tablespace (but not any other symbolic
        links).  This is intended to make sure that all WAL and data files are
        durably stored on disk before replaying changes.  This applies whenever
        starting a database cluster that did not shut down cleanly, including
        copies created with <span class="application">pg_basebackup</span>.
       </p><p>
        On Linux, <code class="literal">syncfs</code> may be used instead, to ask the
        operating system to synchronize the whole file systems that contain the
        data directory, the WAL files and each tablespace (but not any other
        file systems that may be reachable through symbolic links).  This may
        be a lot faster than the <code class="literal">fsync</code> setting, because it
        doesn't need to open each file one by one.  On the other hand, it may
        be slower if a file system is shared by other applications that
        modify a lot of files, since those files will also be written to disk.
        Furthermore, on versions of Linux before 5.8, I/O errors encountered
        while writing data to disk may not be reported to
        <span class="productname">PostgreSQL</span>, and relevant error messages may
        appear only in kernel logs.
       </p><p>
        This parameter can only be set in the
        <code class="filename">postgresql.conf</code> file or on the server command line.
       </p></dd></dl></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="runtime-config-compatible.html" title="20.13. Version and Platform Compatibility">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="runtime-config.html" title="Chapter 20. Server Configuration">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="runtime-config-preset.html" title="20.15. Preset Options">Next</a></td></tr><tr><td width="40%" align="left" valign="top">20.13. Version and Platform Compatibility </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 15.6 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 20.15. Preset Options</td></tr></table></div></body></html>