# tWriteJSONField MapReduce properties (deprecated) Availability-note[Deprecated](https://help.talend.com/r/en-US/Cloud/labels-on-talend-help-center/availability-deprecated) This content is deprecated. These properties are used to configure tWriteJSONField running in the MapReduce Job framework. The MapReduce tWriteJSONField component belongs to the Processing family. The component in this framework is available in all Talend products with Big Data and Talend Data Fabric. Availability-note[Deprecated](https://help.talend.com/r/en-US/Cloud/labels-on-talend-help-center/availability-deprecated) This content is deprecated. The MapReduce framework is deprecated from Talend 7.3 onwards. Use Talend Jobs for Apache Spark to accomplish your integration tasks. ## Basic settings | Output Column | List of the columns defined in the output schema to hold the JSON
field generated. | | --- | --- | | Configure JSON Tree | Opens the interface to create the JSON data structure. For more
information, see [Configuring a JSON Tree](https://help.qlik.com/talend/en-US/components/7.3/processing/configuring-a-json-tree). | | Schema and Edit
Schema | A schema is a row description. It defines the number of fields
(columns) to be processed and passed on to the next component. When you create a Spark
Job, avoid the reserved word line when naming the
fields.

Click Edit
schema to make changes to the schema. If the current schema is of the Repository type, three options are available:

| | | Built-In: You create and store the schema locally for this component
only. | | | Repository: You have already created the schema and stored it in the
Repository. You can reuse it in various projects and Job designs. | | Sync columns | Click to synchronize the output file schema with the input file
schema. The Sync function only displays once the Row connection is
linked with the output component. | | Group by | Define the aggregation set, the columns you want to use to regroup
the data.

Information noteWarning:

Make sure that the data to be grouped is in sequential
order. | | Remove root node | Select this check box to remove the root node from the JSON field
generated. | ## Global Variables | Global Variables | ERROR\_MESSAGE: the error message generated by the component when an
error occurs. This is an After variable and it returns a string. This variable functions
only if the Die on error check box
is cleared, if the component has this check
box.

A Flow variable functions during the execution of a component
while an After variable functions after the execution of the component.

To fill up a field or expression with a
variable, press Ctrl + Space to
access the variable list and choose the variable to use from it.

For further information about variables, see *Talend Studio*
*User Guide*. | | --- | --- | ## Usage | **Usage rule** | In a
Talend
Map/Reduce Job, this component is used as an intermediate
step and other components used along with it must be Map/Reduce components, too. They
generate native Map/Reduce code that can be executed directly in Hadoop.

You need to use the Hadoop Configuration tab in the
Run view to define the connection to a given Hadoop
distribution for the whole Job.

For further information about a
Talend
Map/Reduce Job, see the sections
describing how to create, convert and configure a
Talend
Map/Reduce Job of the
**Talend Big Data Getting Started Guide**.

Note that in this documentation, unless otherwise
explicitly stated, a scenario presents only Standard Jobs,
that is to say traditional
Talend
data integration Jobs, and non Map/Reduce Jobs. | | --- | --- |