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<chapter Id="runtime">

<title>Operating System Environment</title>

<para>

One way to avoid this problem is to run

<productname>PostgreSQL</productname>

on a machine where you can be sure that other processes will not

run the machine out of memory.

<productname>PostgreSQL</productname> on a machine where you can

be sure that other processes will not run the machine out of

memory. If memory is tight, increasing the swap space of the

operating system can help avoiding the problem, because the

out-of-memory (OOM) killer is invoked whenever physical memory and

swap space are exhausted.

</para>

<para>

On Linux 2.6 and later, a better solution is to modify the kernel's

behavior so that it will not <quote>overcommit</> memory. This is

done by selecting strict overcommit mode via <command>sysctl</command>:

On Linux 2.6 and later, an additional measure is to modify the

kernel's behavior so that it will not <quote>overcommit</> memory.

Although this setting will not prevent the OOM killer from

invoking altogether, it will lower the chances significantly and

will therefore lead to more robust system behavior. This is done

by selecting strict overcommit mode via <command>sysctl</command>:

<programlisting>

sysctl -w vm.overcommit_memory=2

</programlisting>