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+$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.166 2003/01/11 05:04:14 momjian Exp $
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<Chapter Id="runtime">
<screen>
IpcSemaphoreCreate: semget(key=5440026, num=16, 01600) failed: No space left on device
</screen>
- does <emphasis>not</emphasis> mean you've run out of disk space. It
- means your kernel's limit on the number of System V semaphores is
- smaller than the number <productname>PostgreSQL</productname> wants
- to create. As above, you may be able to work around the problem by
- starting the postmaster with a reduced number of allowed connections
+ does <emphasis>not</emphasis> mean you've run out of disk
+ space. It means your kernel's limit on the number of <systemitem
+ class="osname">System V</> semaphores is smaller than the number
+ <productname>PostgreSQL</productname> wants to create. As above,
+ you may be able to work around the problem by starting the
+ postmaster with a reduced number of allowed connections
(<option>-N</option> switch), but you'll eventually want to
increase the kernel limit.
</para>
<listitem>
<para>
Sets the number of shared memory buffers used by the database
- server. The default is 64. Each buffer is typically 8192 bytes.
- This option can only be set at server start.
+ server. The default is 64. Each buffer is typically 8192
+ bytes. This must be greater than 16, as well as at least twice
+ the value of <varname>MAX_CONNECTIONS</varname>; however, a
+ higher value can often improve performance on modern
+ machines. Values of at least a few thousand are recommended
+ for production installations. This option can only be set at
+ server start.
+ </para>
+
+ <para>
+ Increasing this parameter may cause <productname>PostgreSQL</>
+ to request more <systemitem class="osname">System V</> shared
+ memory than your operating system's default configuration
+ allows. See <xref linkend="sysvipc"> for information on how to
+ adjust these parameters, if necessary.
</para>
</listitem>
</varlistentry>
<term><varname>WAL_BUFFERS</varname> (<type>integer</type>)</term>
<listitem>
<para>
- Number of disk-page buffers in shared memory for WAL logging.
- This option can only be set at server start.
+ Number of disk-page buffers in shared memory for WAL
+ logging. The default is 4. This option can only be set at
+ server start.
</para>
</listitem>
</varlistentry>