[Tajo Wiki] Update of "Configuration" by HyunsikChoi

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The "Configuration" page has been changed by HyunsikChoi:
http://wiki.apache.org/tajo/Configuration

Comment:
Moved from the site

New page:
== Preliminary ==
Tajo's configuration is based on Hadoop's configuration system. Tajo provides two config files:

 * catalog-site.xml - configuration for the catalog server.
 * tajo-site.xml - configuration for other tajo modules.

Each config consists of a pair of a name and a value. If you want to set the config name a.b.c with the value 123, add the following element to an appropriate file.

{{{
  <property>
    <name>a.b.c</name>
    <value>123</value>
  </property>
}}}

Tajo has a variety of internal configs. If you don't set some config explicitly, the default config will be used for for that config. Tajo is designed to use only a few of configs in usual cases. You may not be concerned with the configuration.

== Setting up catalog-site.xml ==
If you want to customize the catalog service, copy $TAJO_HOME/conf/catalog-site.xml.templete to catalog-site.xml. Then, add the following configs to catalog-site.xml. Note that the default configs are enough to launch Tajo cluster in most cases.

 * catalog.master.addr - If you want to launch a catalog server separately, specify this address. This config has a form of hostname:port. Its default value is localhost:9002.
 * tajo.catalog.store.class - If you want to change the persistent storage of the catalog server, specify the class name. Its default value is tajo.catalog.store.DBStore. In the current version, Tajo provides two persistent storage classes as follows:

  * tajo.catalog.store.DBStore - this storage class uses Apache Derby.
  * tajo.catalog.store.MemStore - this is the in-memory storage. It is only used in unit tests to shorten the duration of unit tests.

== Setting up tajo-site.xml ==

Copy $TAJO_HOME/conf/tajo-site.xml.templete to tajo-site.xml. Then, add the following configs to your tajo-site.xml. '''The following two configs must be set to launch a tajo cluster.'''

{{{
  <property>
    <name>tajo.rootdir</name>
    <value>hdfs://hostname:port/tajo</value>
  </property>

  <property>
    <name>tajo.cluster.distributed</name>
    <value>true</value>
  </property>
}}}

 * tajo.rootdir - Specify the root directory of tajo. This parameter should be a url form (e.g., hdfs://namenode_hostname:port/path). You can also use file:// scheme.

 * tajo.cluster.distributed - It is a flag used internally. It must be true.

The followings are other parameters. DO NOT modify the following configs unless you are an expert of Tajo.

 * tajo.task.localdir
 * tajo.join.task-volume.mb
 * tajo.sort.task-volume.mb
 * tajo.task-aggregation.volume.mb
 * tajo.join.part-volume.mb
 * tajo.sort.part-volume.mb
 * tajo.aggregation.part-volume.mb