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add intro, node groups, and node group links
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@erilong
erilong committed Mar 20, 2008
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xmlns:svg="http://www.w3.org/2000/svg" xmlns:ns="http://docbook.org/ns/docbook"
xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:html="http://www.w3.org/1999/xhtml">
<title>Basic Configuration</title>
<para>
To get an instance of SymmetricDS running, it needs to be given an identity and know how
to connect to the database it will manage. A basic way to specify this is to place properties
in the symmetric.properties file. After connecting to the database, the Node reads its
configuration and current status. If the configuration tables are missing, they are created
automatically, unless that feature is disabled. A basic configuration describes the
following:
<itemizedlist>
<listitem>
<para>Node Groups - each Node belongs to a group</para>
</listitem>
<listitem>
<para>Node Group Links - two Nodes Groups are linked together for synchronization</para>
</listitem>
<listitem>
<para>Nodes - each instance of Symmetric has an identity</para>
</listitem>
<listitem>
<para>Channels - data is categorized to synchronize independently</para>
</listitem>
<listitem>
<para>Triggers - specify which changes in the database are captured</para>
</listitem>
</itemizedlist>
During initialization, the Triggers are verified against the database, and database triggers
are installed on tables that require data changes to be captured. The PullJob and PushJob
begin running as required to synchronize changes with other Nodes.
</para>
<section>
<title>Setting Startup Properties</title>
<para>
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<tbody>
<row>
<entry>
<emphasis>default-symmetric.properties</emphasis>
<emphasis>symmetric-default.properties</emphasis>
</entry>
<entry>Y</entry>
<entry>
Packaged inside symmetric-ds.jar file. This file has all the default
settings and along with descriptions.
settings along with descriptions.
</entry>
</row>
<row>
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</tbody>
</tgroup>
</table>

Also see the appendix on <emphasis>Startup Properties</emphasis> to see all the possible
properties and their defaults.
</para>
</section>
<section>
<title>Basic Properties</title>
<para>
Each Node requires properties that will register it with the network and connect it to
the database. To give a Node its identity, the following properties are used:
Each Node requires properties that will connect it to the database and register
it with a parent Node. To give a Node its identity, the following properties are used:
</para>
<variablelist>
<varlistentry>
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</varlistentry>
</variablelist>
</section>
<section>
<title>Node Groups</title>
<para>
Each Node must belong to a Node Group, a collection of one or more Nodes.
A common use of Node Groups is to describe a level in a hierarchy of data synchronization.
For example, at a retail store chain, there might be a few Nodes that belong to "corp", which
sync with hundreds of Nodes that belong to "store", which sync with thousands of Nodes that
belong to "register".
</para>
<para>
The following SQL statements would create Node Groups for "corp" and "store".

<programlisting>
<![CDATA[insert into sym_node_group (node_group_id, description)
values ('store', 'A retail store node');
insert into sym_node_group (node_group_id, description)
values ('corp', 'A corporate node');]]></programlisting>
</para>
</section>
<section>
<title>Node Group Links</title>
<para>
To establish synchronization between Nodes, two Node Groups are linked together. The direction
of synchronization is determined by specifying a source and target Node Group.
If synchronization should occur in both directions, then two links can be created in opposite
directions. The target Node Group can receive data changes by either push or pull methods.
A push method causes the source Node Group to connect to the target, while a pull method
causes it to wait for the target to connect to it.
</para>
<para>
The following SQL statements links the "corp" and "store" Node Groups for synchronization.
It configures the "store" Nodes to push their data changes to the "corp" Nodes,
and the "corp" Nodes to send changes to "store" Nodes by waiting for a pull.

<programlisting>
<![CDATA[insert into sym_node_group_link
(source_node_group, target_node_group, data_event_action)
values ('store', 'corp', 'P');
insert into sym_node_group_link
(source_node_group, target_node_group, data_event_action)
values ('corp', 'store', 'W');]]></programlisting>
</para>
</section>
<section>
<title>Nodes</title>
<para></para>
<para>
</para>
</section>
<section>
<title>Channels</title>
<para>
</para>
</section>
<section>
<title>Triggers</title>
<para>
</para>
</section>
</chapter>

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