diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index ef2d250c830a9a22439a8ca67dc1d082018de10a..8e1e6bda0e6e6fc60aef38adeded78b4e58c6cea 100644
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -1,5 +1,5 @@
<!--
-$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.41 2000/12/03 14:36:45 petere Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.42 2000/12/17 11:22:00 petere Exp $
-->
<Chapter Id="runtime">
@@ -1300,11 +1300,12 @@ env PGOPTIONS='-c geqo=off' psql
limits of the IPC resources then the postmaster will refuse to
start up and should leave a marginally instructive error message
about which problem was encountered and what needs to be done
- about it. The relevant kernel parameters are named
+ about it. (See also <xref linkend="postmaster-start-failures">.)
+ The relevant kernel parameters are named
consistently across different systems; <xref
linkend="sysvipc-parameters"> gives an overview. The methods to
set them, however, vary; suggestions for some platforms are given
- below. Be aware that you will have to reboot your
+ below. Be aware that you will probably have to reboot your
machine at least, possibly even recompile the kernel, to change these
settings.
</para>
@@ -1332,13 +1333,13 @@ env PGOPTIONS='-c geqo=off' psql
<row>
<entry><varname>SHMMIN</></>
<entry>Minimum size of shared memory segment (bytes)</>
- <entry>1 (at most 144)</>
+ <entry>1 (at most about 256 kB)</>
</row>
<row>
<entry><varname>SHMSEG</></>
<entry>Maximum number of shared memory segments per process</>
- <entry>must be at least 3, but the default is much higher</>
+ <entry>only 1 segment is needed, but the default is much higher</>
</row>
<row>
@@ -1356,13 +1357,13 @@ env PGOPTIONS='-c geqo=off' psql
<row>
<entry><varname>SEMMNS</></>
<entry>Maximum number of semaphores system-wide</>
- <entry>max_connections rounded up to multiple of 16, + room for other applications</>
+ <entry>ceil(max_connections / 16) * 17 + room for other applications</>
</row>
<row>
<entry><varname>SEMMSL</></>
<entry>Maximum number of semaphores per set</>
- <entry>>= 16</>
+ <entry>>= 17</>
</row>
<row>
@@ -1396,34 +1397,36 @@ env PGOPTIONS='-c geqo=off' psql
estimate the required segment size as the number of buffers times
the block size (8192 kB by default) plus ample overhead (at least
half a megabyte). Any error message you might get will contain the
- size of the failed allocation. (<productname>Postgres</> will
- actually use three shared memory segments, but the size of the
- other two is negligible for this consideration.)
+ size of the failed allocation.
</para>
<para>
Less likely to cause problems is the minimum size for shared
- memory segments (<varname>SHMMIN</>), which must be at least 144
- for <productname>Postgres</> (it's usually just 1), and the
- maximum number of segments system-wide (<varname>SHMMNI</>, as
- mentioned, 3 are needed) or per-process (<varname>SHMSEG</>,
- ditto). Some systems also have a limit on the total amount of
- shared memory in the system; see the platform-specific
- instructions below.
+ memory segments (<varname>SHMMIN</>), which should be at most
+ somewhere around 256 kB for <productname>Postgres</> (it is
+ usually just 1). The maximum number of segments system-wide
+ (<varname>SHMMNI</>) or per-process (<varname>SHMSEG</>) should
+ not cause a problem unless your system has them set to zero. Some
+ systems also have a limit on the total amount of shared memory in
+ the system; see the platform-specific instructions below.
</para>
<para>
<productname>Postgres</> uses one semaphore per allowed connection
- (<option>-N</> option), in sets of 16. The maximum number of
- semaphores in the system is set by <varname>SEMMNS</>, which
- consequently must be at least as high as the connection setting.
- The parameter <varname>SEMMNI</> determines the limit on the
- number of semaphore sets that can exist on the system at one time.
- Hence this parameter must be at least
- <literal>ceil(max_connections / 16)</>. Lowering the number of
- allowed connections is a temporary workaround for failures, which
- are usually confusingly worded <quote><errorname>No space left on
- device</></>, from the function <function>semget()</>.
+ (<option>-N</> option), in sets of 16. Each such set will also
+ contain a 17th semaphore which contains a <quote>magic
+ number</quote>, to avoid collision with semaphore sets used by
+ other applications. The maximum number of semaphores in the system
+ is set by <varname>SEMMNS</>, which consequently must be at least
+ as high as the connection setting plus one extra for each 16
+ allowed connections (see the formula in <xref
+ linkend="sysvipc-parameters">. The parameter <varname>SEMMNI</>
+ determines the limit on the number of semaphore sets that can
+ exist on the system at one time. Hence this parameter must be at
+ least <literal>ceil(max_connections / 16)</>. Lowering the number
+ of allowed connections is a temporary workaround for failures,
+ which are usually confusingly worded <quote><errorname>No space
+ left on device</></>, from the function <function>semget()</>.
</para>
<para>
@@ -1441,7 +1444,7 @@ env PGOPTIONS='-c geqo=off' psql
<para>
The <varname>SEMMSL</> parameter, which determines how many
- semaphores can be in a set, must be at least 16 for
+ semaphores can be in a set, must be at least 17 for
<productname>Postgres</>.
</para>
@@ -1558,11 +1561,11 @@ options SEMMAP=256
<varlistentry>
- <term>HPUX</>
+ <term>HP-UX</>
<listitem>
<para>
The default settings tend to suffice for normal installations.
- On <productname>HPUX</> 10, the factory default for
+ On <productname>HP-UX</> 10, the factory default for
<varname>SEMMNS</> is 128, which might be too low for larger
database sites.
</para>
@@ -1581,11 +1584,23 @@ options SEMMAP=256
<term>Linux</>
<listitem>
<para>
- System V IPC is enabled by default and sufficiently sized for
- most uses. The relevant parameters are in
+ The default shared memory limit (both
+ <varname>SHMMAX</varname> and <varname>SHMALL</varname>) is 32
+ MB in 2.2 kernels, but it can be changed in the
+ <filename>proc</filename> file system (without reboot). For
+ example, to allow 128 MB:
+<screen>
+<prompt>$</prompt> <userinput>echo 134217728 >/proc/sys/kernel/shmall</userinput>
+<prompt>$</prompt> <userinput>echo 134217728 >/proc/sys/kernel/shmmax</userinput>
+</screen>
+ You could put these commands into a script run at boot-time.
+ </para>
+
+ <para>
+ Other parameters are sufficiently sized for any application.
+ If you want to see for yourself look into
<filename>/usr/src/linux/include/asm-<replaceable>xxx</>/shmparam.h</>
- and <filename>/usr/src/linux/include/linux/sem.h</>. Be sure
- to do <command>make dep</> before rebuilding the kernel.
+ and <filename>/usr/src/linux/include/linux/sem.h</>.
</para>
</listitem>
</varlistentry>