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PostgreSQL documentation
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<title>Notes</title>
<para>
- To stop a running query use the <literal>SIGINT</literal> signal. To
- tell <command>postgres</command> to reread the configuration file,
- use a <literal>SIGHUP</literal> signal. The
- <command>postmaster</command> uses <literal>SIGTERM</literal>
+ To cancel a running query, send the <literal>SIGINT</literal> signal
+ to the <command>postgres</command> process running that command.
+ </para>
+
+ <para>
+ To tell <command>postgres</command> to reread the configuration file,
+ send a <literal>SIGHUP</literal> signal. Normally it's best to
+ <literal>SIGHUP</literal> the <command>postmaster</command> instead;
+ the <command>postmaster</command> will in turn <literal>SIGHUP</literal>
+ each of its children. But in some cases it might be desirable to have only
+ one <command>postgres</command> process reread the configuration file.
+ </para>
+
+ <para>
+ The <command>postmaster</command> uses <literal>SIGTERM</literal>
to tell a <command>postgres</command> process to quit normally and
<literal>SIGQUIT</literal> to terminate without the normal cleanup.
- These <emphasis>should not</emphasis> be used by users.
+ These signals <emphasis>should not</emphasis> be used by users. It is also
+ unwise to send <literal>SIGKILL</literal> to a <command>postgres</command>
+ process --- the <command>postmaster</command> will interpret this as
+ a crash in <command>postgres</command>, and will force all the sibling
+ <command>postgres</command> processes to quit as part of its standard
+ crash-recovery procedure.
</para>
</refsect1>
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PostgreSQL documentation
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<para>
If at all possible, <emphasis>do not</emphasis> use
<literal>SIGKILL</literal> to kill the
- <command>postmaster</command>. This will prevent
+ <command>postmaster</command>. Doing so will prevent
<command>postmaster</command> from freeing the system
resources (e.g., shared memory and semaphores) that it holds before
- terminating.
+ terminating. This may cause problems for starting a fresh
+ <command>postmaster</command> run.
</para>
<para>