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<?xml version="1.0" encoding="ISO-8859-1"?>
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- Copyright (C) 1998-2018 OpenLink Software
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- under the terms of the GNU General Public License as published by the
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-->
<refentry id="fn_checkpoint_interval">
<refmeta>
<refentrytitle>checkpoint_interval</refentrytitle>
<refmiscinfo>admin</refmiscinfo>
</refmeta>
<refnamediv>
<refname>checkpoint_interval</refname>
<refpurpose>Configure database checkpointing</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis id="fsyn_checkpoint_interval">
<funcprototype id="fproto_checkpoint_interval">
<funcdef>integer <function>checkpoint_interval</function> </funcdef>
<paramdef>in <parameter>minutes</parameter> integer</paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1 id="desc_checkpoint_interval">
<title>Description</title>
<para>This function changes the database checkpointing interval to the given
value in minutes. It may also be used to disable checkpointing in two
ways: By setting checkpoint interval to 0, the checkpoint will only be
performed after roll forward upon database startup. A setting of -1
will disable all checkpointing. Main use for this function is to
ensure a clean online backup of the database slices. Copying of the
database may take long and checkpointing would modify those files in
mid-copy, thus rendering the resulting copy unusable. In case the
system should, for some reason or another, become unstable, it is
sometimes better to disable checkpointing after a database restart
to resume backing up from where it was left prior to a system crash.
Disabling all checkpointing by giving checkpoint_interval the value
of -1 will do just that.</para>
<para>The interval setting will be saved in the server configuration
file as value of CheckpointInterval in section [Parameters], thus it
will persist over consecutive server shutdown/restart cycles. A
long checkpoint_interval setting will produce longer transaction
logs, which in turn prolongs the time it takes for the database to
perform a roll forward upon restart in case it was shut down without
making a checkpoint.</para>
</refsect1>
<refsect1 id="params_checkpoint_interval"><title>Parameters</title>
<refsect2><title>minutes</title>
<para><type>integer</type> number of minutes between checkpoints.</para></refsect2>
</refsect1>
<refsect1 id="ret_checkpoint_interval"><title>Return Types</title>
<para>Previous value of CheckpointInterval in the configuration file as an integer.</para>
</refsect1>
<refsect1 id="errors_checkpoint_interval"><title>Errors</title>
<para><link linkend="datatypeerror">Parameter data type checking errors</link></para>
</refsect1>
<refsect1 id="examples_checkpoint_interval"><title>Examples</title>
<example id="ex_checkpoint_interval"><title>Simple examples</title>
<para>Disable checkpoints:</para>
<screen>SQL> checkpoint_interval(-1);
Done. -- 25 msec.
</screen>
<para>Re-enable checkpoints (every 2 hrs):</para>
<screen>SQL> checkpoint_interval(120);
callret
VARCHAR
______________________________________________________
-1
Done. -- 4 msec.
</screen>
</example>
</refsect1>
<refsect1 id="seealso_checkpoint_interval"><title>See Also</title>
<para><link linkend="fn_backup"><function>backup</function></link></para>
<para><link linkend="configsrvstupfiles">CheckpointInterval setting in Configuring Server Startup Files section</link></para>
</refsect1>
</refentry>
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