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<chapter Id="runtime-config">

<title>Server Configuration</title>

Sets the maximum number of disk pages for which free space will

be tracked in the shared free-space map. Six bytes of shared memory

are consumed for each page slot. This setting must be more than

16 * <varname>max_fsm_relations</varname>. The default is20000,

but<application>initdb</>will try to set it as close as possible

to 200000, depending on the amount of available memory.

This option can only be set at server start.

16 * <varname>max_fsm_relations</varname>. The default ischosen

by<application>initdb</>depending on the amount of available memory,

and can range from 20000 to 200000.

This option can only be set at server start.

</para>

</listitem>

</varlistentry>

Controls whether the server should start the

statistics-collection subprocess. This is on by default, but

may be turned off if you know you have no interest in

collecting statistics. This option can only be set at server

start.

collecting statistics or running autovacuum.

This option can only be set at server start, because the collection

subprocess cannot be started or stopped on-the-fly. (However, the

extent to which statistics are actually gathered can be changed while

the server is running, so long as the subprocess exists.)

</para>

</listitem>

</varlistentry>

<indexterm>

<primary>autovacuum</primary>

<secondary>globalconfiguration parameters</secondary>

<secondary>configuration parameters</secondary>

</indexterm>

<para>

These settings control thedefaultbehaviorfor the <firstterm>autovacuum

daemon</firstterm>. Please refer to <xref linkend="autovacuum"> for

These settings control the behaviorof the <firstterm>autovacuum</>

feature. Please refer to <xref linkend="autovacuum"> for

more information.

</para>

</indexterm>

<listitem>

<para>

Controls whether the server shouldstart the

autovacuumsubprocess. This is off by default.

Controls whether the server shouldrun the

autovacuumdaemon. This is off by default.

<varname>stats_start_collector</> and <varname>stats_row_level</>

must also be on forthis tostart.

must also beturnedon forautovacuum towork.

This option can only be set at server start or in the

<filename>postgresql.conf</filename> file.

</para>

<listitem>

<para>

Specifies the delay between activity rounds for the autovacuum

subprocess. In each round thesubprocess examines one database

daemon. In each round thedaemon examines one database

and issues <command>VACUUM</> and <command>ANALYZE</> commands

as needed for tables in that database. The delay is measured

in seconds, and the default is 60.