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<?xml version="1.0" encoding="ISO-8859-1"?>
<!--
-
- This file is part of the OpenLink Software Virtuoso Open-Source (VOS)
- project.
-
- Copyright (C) 1998-2018 OpenLink Software
-
- This project is free software; you can redistribute it and/or modify it
- under the terms of the GNU General Public License as published by the
- Free Software Foundation; only version 2 of the License, dated June 1991.
-
- This program is distributed in the hope that it will be useful, but
- WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- General Public License for more details.
-
- You should have received a copy of the GNU General Public License along
- with this program; if not, write to the Free Software Foundation, Inc.,
- 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
-
-
-->
<refentry id="fn_SYS_DB_STAT">
<refmeta>
<refentrytitle>SYS_DB_STAT</refentrytitle>
<refmiscinfo>stat</refmiscinfo>
</refmeta>
<refnamediv>
<refname>SYS_DB_STAT</refname>
<refpurpose>gathers common statistical information about the database.</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis id="fsyn_SYS_DB_STAT">
<funcprototype id="fproto_SYS_DB_STAT">
<funcdef> <function>SYS_DB_STAT</function></funcdef>
<paramdef>in <parameter>pcnt</parameter> integer</paramdef>
<paramdef>in <parameter>ignore_vdb</parameter> integer</paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1 id="desc_SYS_DB_STAT">
<title>Description</title>
<para>The <computeroutput>SYS_DB_STAT</computeroutput> procedure gathers common
information about the whole Virtuoso database, including attached remote tables. It traverses
each table and populates the SYS_COL_STAT table with data collected. SYS_DB_STAT can
be used in random mode when not all rows of the tables are used to gather statistics
of the database.</para>
<para><computeroutput>SYS_DB_STAT</computeroutput> gathers the following information
for each column, COL, traversed in the database:</para>
<simplelist>
<member>SYS_COL_STAT - SQL command </member>
<member>CS_N_DISTINCT - count (distinct XXX)</member>
<member>CS_MIN - min (XXX)</member>
<member>CS_MAX - max (XXX)</member>
<member>CS_AVG_LEN - avg (raw_length (XXX))</member>
<member>CS_N_VALUES - count (XXX)</member>
<member>CS_N_ROWS - count (XXX)</member>
</simplelist>
</refsect1>
<refsect1 id="params_SYS_DB_STAT"><title>Parameters</title>
<refsect2><title>pcnt</title>
<para>Rate that affects percentage of database coverage. Zero means that the whole database is read. The default is 5, for a random sample of approximately 5 percent of each table.</para>
</refsect2>
<refsect2><title>ignore_vdb</title>
<para>By default SYS_DB_STAT does not analyze the remote tables. To
allow statistics gathering over linked tables, set this parameter to zero.
Remote tables can be very large or access to them can be very slow or both.
If this parameter is set to zero and pcnt is zero, SYS_DB_STAT will read the remote tables from start to end which may take very long. If pcnt is non-zero, this function will use its knowledge of the remote DBMS to get statistics in a DBMS specific manner if the DBMS is supported. See sys_stat_vdb_mappers table.</para></refsect2>
</refsect1>
<refsect1 id="ret_SYS_DB_STAT"><title>Return Types</title>
<para>None.</para>
</refsect1>
<!--
<refsect1 id="errors_SYS_DB_STAT">
<title>Errors</title>
<para>This function can generate the following errors:</para>
<errorcode></errorcode>
</refsect1>
-->
<!-- refsect1 id="examples_SYS_DB_STAT">
<title>Examples</title>
<example id="ex_"><title />
<para />
<screen>
</screen>
</example>
</refsect1 -->
<refsect1 id="seealso_SYS_DB_STAT">
<title>See Also</title>
<para><link linkend="fn_sys_stat_histogram">sys_stat_histogram</link></para>
<para><link linkend="fn_sys_stat_analyze">sys_stat_analyze</link></para>
</refsect1>
</refentry>
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