ways to change these parameters.

</para>

<para>

This view does not display <link linkend="runtime-config-custom">customized options</link>

until the extension module that defines them has been loaded.

</para>

<para>

This view cannot be inserted into or deleted from, but it can be updated. An

<command>UPDATE</command> applied to a row of <structname>pg_settings</structname>

<command>SET</command>.

</para>

<para>

This view does not

display <link linkend="runtime-config-custom">customized options</link>

unless the extension module that defines them has been loaded by the

backend process executing the query (e.g., via a mention in

<xref linkend="guc-shared-preload-libraries"/>,

a call to a C function in the extension, or the

<link linkend="sql-load"><command>LOAD</command></link> command).

For example, since <link linkend="archive-modules">archive modules</link>

are normally loaded only by the archiver process not regular sessions,

this view will not display any customized options defined by such modules

unless special action is taken to load them into the backend process

executing the query.

</para>

</sect1>

<sect1 id="view-pg-shadow">