</para>

<para>

<literal>timezone_abbreviations</> can be set to any file name

<varname>timezone_abbreviations</> can be set to any file name

found in <filename>.../share/timezonesets/</>, if the file's name

is entirely alphabetic. (The prohibition against non-alphabetic

characters in <literal>timezone_abbreviations</> prevents reading

characters in <varname>timezone_abbreviations</> prevents reading

files outside the intended directory, as well as reading editor

backup files and other extraneous files.)

</para>

according to the <literal>zoneinfo</> timezone database. The zone name

definitions found in these files can be copied and pasted into a custom

configuration file as needed. Note that these files cannot be directly

referenced as <literal>timezone_abbreviations</> settings, because of

referenced as <varname>timezone_abbreviations</> settings, because of

the dot embedded in their names.

</para>

<para>

Parameters reported as of the current release include

<literal>server_version</>,

<literal>server_encoding</>,

<literal>client_encoding</>,

<literal>application_name</>,

<literal>is_superuser</>,

<literal>session_authorization</>,

<literal>DateStyle</>,

<literal>IntervalStyle</>,

<literal>TimeZone</>,

<literal>integer_datetimes</>, and

<literal>standard_conforming_strings</>.

(<literal>server_encoding</>, <literal>TimeZone</>, and

<literal>integer_datetimes</> were not reported by releases before 8.0;

<literal>standard_conforming_strings</> was not reported by releases

<varname>server_version</>,

<varname>server_encoding</>,

<varname>client_encoding</>,

<varname>application_name</>,

<varname>is_superuser</>,

<varname>session_authorization</>,

<varname>DateStyle</>,

<varname>IntervalStyle</>,

<varname>TimeZone</>,

<varname>integer_datetimes</>, and

<varname>standard_conforming_strings</>.

(<varname>server_encoding</>, <varname>TimeZone</>, and

<varname>integer_datetimes</> were not reported by releases before 8.0;

<varname>standard_conforming_strings</> was not reported by releases

before 8.1;

<literal>IntervalStyle</> was not reported by releases before 8.4;

<literal>application_name</> was not reported by releases before 9.0.)

<varname>IntervalStyle</> was not reported by releases before 8.4;

<varname>application_name</> was not reported by releases before 9.0.)

Note that

<literal>server_version</>,

<literal>server_encoding</> and

<literal>integer_datetimes</>

<varname>server_version</>,

<varname>server_encoding</> and

<varname>integer_datetimes</>

cannot change after startup.

</para>

<para>

Pre-3.0-protocol servers do not report parameter settings, but

<application>libpq</> includes logic to obtain values for

<literal>server_version</> and <literal>client_encoding</> anyway.

<varname>server_version</> and <varname>client_encoding</> anyway.

Applications are encouraged to use <function>PQparameterStatus</>

rather than <foreignphrase>ad hoc</> code to determine these values.

(Beware however that on a pre-3.0 connection, changing

<literal>client_encoding</> via <command>SET</> after connection

<varname>client_encoding</> via <command>SET</> after connection

startup will not be reflected by <function>PQparameterStatus</>.)

For <literal>server_version</>, see also

For <varname>server_version</>, see also

<function>PQserverVersion</>, which returns the information in a

numeric form that is much easier to compare against.

</para>

<para>

If no value for <literal>standard_conforming_strings</> is reported,

If no value for <varname>standard_conforming_strings</> is reported,

applications can assume it is <literal>off</>, that is, backslashes

are treated as escapes in string literals. Also, the presence of

this parameter can be taken as an indication that the escape string

autovacuum will only touch the table if it must do so

to prevent transaction ID wraparound.

Another two parameters,

<literal>autovacuum_vacuum_cost_delay</literal> and

<literal>autovacuum_vacuum_cost_limit</literal>, are used to set

<varname>autovacuum_vacuum_cost_delay</> and

<varname>autovacuum_vacuum_cost_limit</>, are used to set

table-specific values for the cost-based vacuum delay feature

(see <xref linkend="runtime-config-resource-vacuum-cost">).

<literal>autovacuum_freeze_min_age</literal>,

<literal>autovacuum_freeze_max_age</literal> and

<literal>autovacuum_freeze_table_age</literal> are used to set

<varname>autovacuum_freeze_min_age</>,

<varname>autovacuum_freeze_max_age</> and

<varname>autovacuum_freeze_table_age</> are used to set

values for <xref linkend="guc-vacuum-freeze-min-age">,

<xref linkend="guc-autovacuum-freeze-max-age"> and

<xref linkend="guc-vacuum-freeze-table-age"> respectively.

A better approach is to send the server's

<systemitem>stderr</> output to some type of log rotation program.

There is a built-in log rotation facility, which you can use by

setting the configuration parameter <literal>logging_collector</> to

setting the configuration parameter <varname>logging_collector</> to

<literal>true</> in <filename>postgresql.conf</>. The control

parameters for this program are described in <xref

linkend="runtime-config-logging-where">. You can also use this approach

Another production-grade approach to managing log output is to

send it to <application>syslog</> and let

<application>syslog</> deal with file rotation. To do this, set the

configuration parameter <literal>log_destination</> to <literal>syslog</>

configuration parameter <varname>log_destination</> to <literal>syslog</>

(to log to <application>syslog</> only) in

<filename>postgresql.conf</>. Then you can send a <literal>SIGHUP</literal>

signal to the <application>syslog</> daemon whenever you want to force it

archive_cleanup_command = 'pg_archivecleanup -d /mnt/standby/archive %r 2>>cleanup.log'

</programlisting>

where the archive directory is physically located on the standby server,

so that the <literal>archive_command</> is accessing it across NFS,

so that the <varname>archive_command</> is accessing it across NFS,

but the files are local to the standby.

This will:

</para>

<para>

<application>pg_standby</> is designed to be a waiting

<literal>restore_command</literal>, which is needed to turn a standard

<varname>restore_command</>, which is needed to turn a standard

archive recovery into a warm standby operation. Other

configuration is required as well, all of which is described in the main

server manual (see <xref linkend="warm-standby">).

<synopsis>

pg_standby <optional> <replaceable>option</> ... </optional> <replaceable>archivelocation</> <replaceable>nextwalfile</> <replaceable>xlogfilepath</> <optional> <replaceable>restartwalfile</> </optional>

</synopsis>

When used within <literal>restore_command</literal>, the <literal>%f</> and

When used within <varname>restore_command</>, the <literal>%f</> and

<literal>%p</> macros should be specified for <replaceable>nextwalfile</>

and <replaceable>xlogfilepath</> respectively, to provide the actual file

and path required for the restore.

recovery_end_command = 'rm -f /tmp/pgsql.trigger.5442'

</programlisting>

where the archive directory is physically located on the standby server,

so that the <literal>archive_command</> is accessing it across NFS,

so that the <varname>archive_command</> is accessing it across NFS,

but the files are local to the standby (enabling use of <literal>ln</>).

This will:

<itemizedlist>

recovery_end_command = 'del C:\pgsql.trigger.5442'

</programlisting>

Note that backslashes need to be doubled in the

<literal>archive_command</>, but <emphasis>not</emphasis> in the

<literal>restore_command</> or <literal>recovery_end_command</>.

<varname>archive_command</>, but <emphasis>not</emphasis> in the

<varname>restore_command</> or <varname>recovery_end_command</>.

This will:

<itemizedlist>

<listitem>

</para>

<para>

<productname>PostgreSQL</> 8.4 provides the

<literal>recovery_end_command</literal> option. Without this option

<varname>recovery_end_command</> option. Without this option

a leftover trigger file can be hazardous.

</para>

</sect2>

<para>

At present there is a hard-wired set of parameters for which

ParameterStatus will be generated: they are

<literal>server_version</>,

<literal>server_encoding</>,

<literal>client_encoding</>,

<literal>application_name</>,

<literal>is_superuser</>,

<literal>session_authorization</>,

<literal>DateStyle</>,

<literal>IntervalStyle</>,

<literal>TimeZone</>,

<literal>integer_datetimes</>, and

<literal>standard_conforming_strings</>.

(<literal>server_encoding</>, <literal>TimeZone</>, and

<literal>integer_datetimes</> were not reported by releases before 8.0;

<literal>standard_conforming_strings</> was not reported by releases

<varname>server_version</>,

<varname>server_encoding</>,

<varname>client_encoding</>,

<varname>application_name</>,

<varname>is_superuser</>,

<varname>session_authorization</>,

<varname>DateStyle</>,

<varname>IntervalStyle</>,

<varname>TimeZone</>,

<varname>integer_datetimes</>, and

<varname>standard_conforming_strings</>.

(<varname>server_encoding</>, <varname>TimeZone</>, and

<varname>integer_datetimes</> were not reported by releases before 8.0;

<varname>standard_conforming_strings</> was not reported by releases

before 8.1;

<literal>IntervalStyle</> was not reported by releases before 8.4;

<literal>application_name</> was not reported by releases before 9.0.)

<varname>IntervalStyle</> was not reported by releases before 8.4;

<varname>application_name</> was not reported by releases before 9.0.)

Note that

<literal>server_version</>,

<literal>server_encoding</> and

<literal>integer_datetimes</>

<varname>server_version</>,

<varname>server_encoding</> and

<varname>integer_datetimes</>

are pseudo-parameters that cannot change after startup.

This set might change in the future, or even become configurable.

Accordingly, a frontend should simply ignore ParameterStatus for

<para>

The database activity of <application>pg_dump</application> is

normally collected by the statistics collector. If this is

undesirable, you can set parameter <literal>track_counts</literal>

undesirable, you can set parameter <varname>track_counts</>

to false via <envar>PGOPTIONS</envar> or the <literal>ALTER

USER</literal> command.

</para>