The agent in the Pega-EndUserUI ruleset performs periodic purging of orphan tags from the database table pr_data_tag.
Orphan tags are tags that exist in the table, but are not linked to any work objects and are not designated as seed tags. A tag becomes an orphan if a user deletes the tag from the work object and the tag is not associated with any other work objects. For example, if a user misspelled a tag, deleted it, and created a new tag with the correct spelling, the original misspelled tag, if it were not associated with another work object, would be an orphan tag.
Deleting a tag from a work object deletes the link from the tag to the work object; it does not delete the tag. The agent deletes the tag from the table.
Seed tags, configured by developers using the Tag Configuration tab on the Social landing page, are not purged by the agent. Seed tags can be deleted using the Tag Configuration tab.