2. Enable Tez AM

	Warning
	These instructions are now obsolete and no longer provide a Supported version of Tez. Use the information found in HDP 2.1 regarding Installing and Configuring Tez.

Use the following instructions to enable Tez AM:

On all the client nodes and Tez Service host machine, edit /etc/tez/conf/tez-env.sh file and modify the following environment variables:
```
export HADOOP_HOME="$HADOOP_HOME"
export JAVA_HOME="$JAVA_HOME"       
```
where
- $HADOOP_HOME is the location of the directory that contains all core Hadoop JAR files. For example, /usr/lib/hadoop.
- $JAVA_HOME is the location of the directory that contains JDK.
Ensure that the /$HADOOP_HOME/bin/hadoop file exists on the Tez Service host machine.

On all the client nodes and Tez host machine, edit mapred-site.xml and modify the following properties:

Enable Tez AM:

<property>    
    <name>mapreduce.framework.name</name>    
    <value>yarn-tez</value>    
    <description>Name of the MapReduce framework. Default value is yarn.</description>  
</property>

Set MapReduce CLASSPATH to a CLASSPATH that contains all the Tez JAR files:
```
<property>    
    <name>mapreduce.application.classpath</name>    
    <value>$TEZ_HOME/*,$TEZ_HOME/lib/*</value>    
    <description>Classpath for MapReduce applications.</description>  
</property> 
```
where $TEZ_HOME is the location of the directory that contains all the Tez JAR files. By default, $TEZ_HOME is set to /usr/lib/tez.

Enable container reuse across task attempts:

<property>    
    <name>yarn.app.mapreduce.am.scheduler.reuse.enable</name>    
    <value>true</value>    
    <description>Enable container reuse across task attempts. Default is set to false.</description>  
</property>

Define number of task attempts to be run on a single container before the container is released. Use -1 to disable this limit.

<property>    
    <name>yarn.app.mapreduce.am.scheduler.reuse.max-attempts-per-container</name>    
    <value>-1</value>    
    <description>Defines number of task attempts to be run on a single container before the container is
            released. To disable this limit, set the value of this property to -1.</description>  
</property>

	Note
	For certain workloads, some jobs tend to have memory leaks and so we recommend that you set the container reuse property to a manageable value (for example 5 or 10).

On all the client nodes and Tez hostmachine, edit hadoop-env.sh and set HADOOP_CLASSPATH as shown below:
```
export HADOOP_CLASSPATH=$HADOOP_CLASSPATH:$TEZ_HOME/*:$TEZ_HOME/lib/*
```
where, $TEZ_HOME is the location of the directory that contains all the Tez JAR files. By default, $TEZ_HOME is set to /usr/lib/tez.

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