!What does the [{$pagename}] do? 

The [{$pagename}] applies to both the Subscriber channel and to the Publisher channel. 

The purpose of the [{$pagename}] is to perform a preliminary transformation on all XML documents sent to Identity Manager by the driver and returned to Identity Manager from the driver. The Input Transformation Policy is applied to the XML documents sent to XmlCommandProcessor.execute and XmlQueryProcessor.query (when called by the driver) and to the XML documents returned from SubscriptionShim.execute, and XmlQueryProcessor.query (when called by Identity Manager). 

The [{$pagename}] is applied before the [Schema Mapping Policy].

The [{$pagename}] uses the [Policy Set Interval Values] of 1. 

The [{$pagename}] is often used to transform data from the application format into the Identity Vault format. When the [{$pagename}] is used for data format transformations the Output Transformation Policy usually performs the data transformation in the opposite direction (i.e., transforms from the Identity Vault format to the application format). The Input Transformation Policy is also used to perform actions in response to the results of commands sent to the shim. 

__Note__ that schema names will always be in the [application namespace] in the XML processed by the [Input Transformation Policy Set].

It is also possible to use the [{$pagename}] to transform an arbitrary XML format native to the connected application to the format expected by Identity Manager. Such transformations must be written in XSLT because DirXML-Script operates only on the Identity Manager-specific XML vocabulary. 

[{$pagename}] primarily handle the conversion of data formats from data that the application shim provides to data that the Metadirectory engine expects. Examples of these conversions include: 
* Attribute value format conversion 
* XML vocabulary conversion 
* Driver heartbeat 
* Custom handling of status messages returned from the application shim to the Metadirectory engine 

All documents supplied to the Metadirectory engine by the application shim on either channel pass through the [{$pagename}]. 

!! More Information
There might be more information for this subject on one of the following:
[{ReferringPagesPlugin before='*' after='\n' }]