<?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>19.15. Preset Options</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-error-handling.html" title="19.14. Error Handling" /><link rel="next" href="runtime-config-custom.html" title="19.16. Customized Options" /></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">19.15. Preset Options</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="runtime-config-error-handling.html" title="19.14. Error Handling">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="runtime-config.html" title="Chapter 19. Server Configuration">Up</a></td><th width="60%" align="center">Chapter 19. Server Configuration</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 11.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="runtime-config-custom.html" title="19.16. Customized Options">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="RUNTIME-CONFIG-PRESET"><div class="titlepage"><div><div><h2 class="title" style="clear: both">19.15. Preset Options</h2></div></div></div><p> The following <span class="quote">“<span class="quote">parameters</span>”</span> are read-only, and are determined when <span class="productname">PostgreSQL</span> is compiled or when it is installed. As such, they have been excluded from the sample <code class="filename">postgresql.conf</code> file. These options report various aspects of <span class="productname">PostgreSQL</span> behavior that might be of interest to certain applications, particularly administrative front-ends. </p><div class="variablelist"><dl class="variablelist"><dt id="GUC-BLOCK-SIZE"><span class="term"><code class="varname">block_size</code> (<code class="type">integer</code>) <a id="id-1.6.6.18.3.1.1.3" class="indexterm"></a> </span></dt><dd><p> Reports the size of a disk block. It is determined by the value of <code class="literal">BLCKSZ</code> when building the server. The default value is 8192 bytes. The meaning of some configuration variables (such as <a class="xref" href="runtime-config-resource.html#GUC-SHARED-BUFFERS">shared_buffers</a>) is influenced by <code class="varname">block_size</code>. See <a class="xref" href="runtime-config-resource.html" title="19.4. Resource Consumption">Section 19.4</a> for information. </p></dd><dt id="GUC-DATA-CHECKSUMS"><span class="term"><code class="varname">data_checksums</code> (<code class="type">boolean</code>) <a id="id-1.6.6.18.3.2.1.3" class="indexterm"></a> </span></dt><dd><p> Reports whether data checksums are enabled for this cluster. See <a class="xref" href="app-initdb.html#APP-INITDB-DATA-CHECKSUMS">data checksums</a> for more information. </p></dd><dt id="GUC-DATA-DIRECTORY-MODE"><span class="term"><code class="varname">data_directory_mode</code> (<code class="type">integer</code>) <a id="id-1.6.6.18.3.3.1.3" class="indexterm"></a> </span></dt><dd><p> On Unix systems this parameter reports the permissions of the data directory defined by (<a class="xref" href="runtime-config-file-locations.html#GUC-DATA-DIRECTORY">data_directory</a>) at startup. (On Microsoft Windows this parameter will always display <code class="literal">0700</code>). See <a class="xref" href="app-initdb.html#APP-INITDB-ALLOW-GROUP-ACCESS">group access</a> for more information. </p></dd><dt id="GUC-DEBUG-ASSERTIONS"><span class="term"><code class="varname">debug_assertions</code> (<code class="type">boolean</code>) <a id="id-1.6.6.18.3.4.1.3" class="indexterm"></a> </span></dt><dd><p> Reports whether <span class="productname">PostgreSQL</span> has been built with assertions enabled. That is the case if the macro <code class="symbol">USE_ASSERT_CHECKING</code> is defined when <span class="productname">PostgreSQL</span> is built (accomplished e.g. by the <code class="command">configure</code> option <code class="option">--enable-cassert</code>). By default <span class="productname">PostgreSQL</span> is built without assertions. </p></dd><dt id="GUC-INTEGER-DATETIMES"><span class="term"><code class="varname">integer_datetimes</code> (<code class="type">boolean</code>) <a id="id-1.6.6.18.3.5.1.3" class="indexterm"></a> </span></dt><dd><p> Reports whether <span class="productname">PostgreSQL</span> was built with support for 64-bit-integer dates and times. As of <span class="productname">PostgreSQL</span> 10, this is always <code class="literal">on</code>. </p></dd><dt id="GUC-LC-COLLATE"><span class="term"><code class="varname">lc_collate</code> (<code class="type">string</code>) <a id="id-1.6.6.18.3.6.1.3" class="indexterm"></a> </span></dt><dd><p> Reports the locale in which sorting of textual data is done. See <a class="xref" href="locale.html" title="23.1. Locale Support">Section 23.1</a> for more information. This value is determined when a database is created. </p></dd><dt id="GUC-LC-CTYPE"><span class="term"><code class="varname">lc_ctype</code> (<code class="type">string</code>) <a id="id-1.6.6.18.3.7.1.3" class="indexterm"></a> </span></dt><dd><p> Reports the locale that determines character classifications. See <a class="xref" href="locale.html" title="23.1. Locale Support">Section 23.1</a> for more information. This value is determined when a database is created. Ordinarily this will be the same as <code class="varname">lc_collate</code>, but for special applications it might be set differently. </p></dd><dt id="GUC-MAX-FUNCTION-ARGS"><span class="term"><code class="varname">max_function_args</code> (<code class="type">integer</code>) <a id="id-1.6.6.18.3.8.1.3" class="indexterm"></a> </span></dt><dd><p> Reports the maximum number of function arguments. It is determined by the value of <code class="literal">FUNC_MAX_ARGS</code> when building the server. The default value is 100 arguments. </p></dd><dt id="GUC-MAX-IDENTIFIER-LENGTH"><span class="term"><code class="varname">max_identifier_length</code> (<code class="type">integer</code>) <a id="id-1.6.6.18.3.9.1.3" class="indexterm"></a> </span></dt><dd><p> Reports the maximum identifier length. It is determined as one less than the value of <code class="literal">NAMEDATALEN</code> when building the server. The default value of <code class="literal">NAMEDATALEN</code> is 64; therefore the default <code class="varname">max_identifier_length</code> is 63 bytes, which can be less than 63 characters when using multibyte encodings. </p></dd><dt id="GUC-MAX-INDEX-KEYS"><span class="term"><code class="varname">max_index_keys</code> (<code class="type">integer</code>) <a id="id-1.6.6.18.3.10.1.3" class="indexterm"></a> </span></dt><dd><p> Reports the maximum number of index keys. It is determined by the value of <code class="literal">INDEX_MAX_KEYS</code> when building the server. The default value is 32 keys. </p></dd><dt id="GUC-SEGMENT-SIZE"><span class="term"><code class="varname">segment_size</code> (<code class="type">integer</code>) <a id="id-1.6.6.18.3.11.1.3" class="indexterm"></a> </span></dt><dd><p> Reports the number of blocks (pages) that can be stored within a file segment. It is determined by the value of <code class="literal">RELSEG_SIZE</code> when building the server. The maximum size of a segment file in bytes is equal to <code class="varname">segment_size</code> multiplied by <code class="varname">block_size</code>; by default this is 1GB. </p></dd><dt id="GUC-SERVER-ENCODING"><span class="term"><code class="varname">server_encoding</code> (<code class="type">string</code>) <a id="id-1.6.6.18.3.12.1.3" class="indexterm"></a> <a id="id-1.6.6.18.3.12.1.4" class="indexterm"></a> </span></dt><dd><p> Reports the database encoding (character set). It is determined when the database is created. Ordinarily, clients need only be concerned with the value of <a class="xref" href="runtime-config-client.html#GUC-CLIENT-ENCODING">client_encoding</a>. </p></dd><dt id="GUC-SERVER-VERSION"><span class="term"><code class="varname">server_version</code> (<code class="type">string</code>) <a id="id-1.6.6.18.3.13.1.3" class="indexterm"></a> </span></dt><dd><p> Reports the version number of the server. It is determined by the value of <code class="literal">PG_VERSION</code> when building the server. </p></dd><dt id="GUC-SERVER-VERSION-NUM"><span class="term"><code class="varname">server_version_num</code> (<code class="type">integer</code>) <a id="id-1.6.6.18.3.14.1.3" class="indexterm"></a> </span></dt><dd><p> Reports the version number of the server as an integer. It is determined by the value of <code class="literal">PG_VERSION_NUM</code> when building the server. </p></dd><dt id="GUC-WAL-BLOCK-SIZE"><span class="term"><code class="varname">wal_block_size</code> (<code class="type">integer</code>) <a id="id-1.6.6.18.3.15.1.3" class="indexterm"></a> </span></dt><dd><p> Reports the size of a WAL disk block. It is determined by the value of <code class="literal">XLOG_BLCKSZ</code> when building the server. The default value is 8192 bytes. </p></dd><dt id="GUC-WAL-SEGMENT-SIZE"><span class="term"><code class="varname">wal_segment_size</code> (<code class="type">integer</code>) <a id="id-1.6.6.18.3.16.1.3" class="indexterm"></a> </span></dt><dd><p> Reports the size of write ahead log segments. The default value is 16MB. See <a class="xref" href="wal-configuration.html" title="30.4. WAL Configuration">Section 30.4</a> for more information. </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-error-handling.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="runtime-config.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="runtime-config-custom.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">19.14. Error Handling </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> 19.16. Customized Options</td></tr></table></div></body></html>