[[Simple_configuration_subsystems]]
= Simple configuration subsystems

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The following subsystems currently have no configuration beyond its root
element in the configuration

[source,xml,options="nowrap"]
----
<subsystem xmlns="urn:jboss:domain:jdr:1.0"/>
<subsystem xmlns="urn:jboss:domain:mvc-krazo:1.0"/>
<subsystem xmlns="urn:jboss:domain:pojo:1.0"/>
<subsystem xmlns="urn:jboss:domain:sar:1.0"/>
----

The presence of each of these turns on a piece of functionality:

[cols=",",options="header"]
|=======================================================================
|Name |Description

|jdr |Enables the gathering of diagnostic data for use in remote
analysis of error conditions. Although the data is in a simple format
and could be useful to anyone, it is primarily useful for JBoss EAP
subscribers who would provide the data to Red Hat when requesting
support.

|mvc-krazo| Provides support for use of Jakarta MVC in deployments. Currently only provided in WildFly Preview, although `preview` stability level support can be added to standard WildFly by including the link:https://github.com/wildfly-extras/mvc-krazo-feature-pack/blob/main/README.md[`wildfly-mvc-krazo-feature-pack`] Galleon feature pack in your server provisioning configuration.

|pojo |Enables the deployment of applications containing JBoss
Microcontainer services, as supported by previous versions of JBoss
Application Server.

|sar |Enables the deployment of .SAR archives containing MBean services,
as supported by previous versions of JBoss Application Server.
|=======================================================================
