<message_body>
<pm:set_user_param>
<user_name>mikem</user_name>
<param datatype="i" name="hostid">i2b2.org</param>
</pm:set_user_param>
</message_body>

A setUserParam message is sent by a client application or another cell service to add a user parameter to the PM cell. The user needs to exist prior to calling this service. If the user and parameter name already exist, the record will be updated.
The domain, username, and password are sent in the header of the message so it does not need to be sent separately in the <message_body>.