The DistributorSender needs to generate a unique file name for each file it sends. The usual way to do this is to concatenate the repository ID with the value of a repository item property. The name of this repository item property is specified by the contentItemNameProperty property of the DistributorSender.

For example, you might have a content item type defined like this:

<item-descriptor name="articles">
     <table name="articles" type="primary" id-column-name="article_id">
     <property name="id" column-name="article_id"/>
     <property name="description"/>

You can set contentItemNameProperty=id, and the DistributorSender uses the id property in creating a unique file name for a repository item of type articles.