Recurring billing companies need to refer to cardholder information on a regular basis. During recurring billing process this information often needs to be updated. Consequently, any recurring billing company must have some account updater functionality at hand. Account updaters can belong to one of the three models.

Three models:

file-based model: a merchant sends a file, containing card numbers and later gets back another file, containing updated card numbers (if updates are relevant and available).
subscription-based model: a merchant subscribes to a service, which, on a regular basis, sends him updates for all accounts listed in the subscription.
integration model: a merchant sends transactions for processing and if any accounts need to be updated, updates are added to responses, which the merchant gets back.

More information on account updater models is available in the respective post on Paylosophy.