This topic provides information about subscription processing, characteristics of a delivered report, and triggering a subscription.
Subscription Processing Overview
Reporting Services includes the Scheduling and Delivery Processor, which provides functionality for scheduling reports and delivering them to users. The report server responds to events that it monitors on an ongoing basis. When an event occurs that matches the conditions defined for a subscription, the report server reads the subscription to determine how to process and deliver the report. The report server requests the delivery extension that is specified in the subscription. After the delivery extension is running, the report server extracts delivery information from the subscription and passes it to the delivery extension for processing.
The delivery extension renders the report in the format defined in the subscription and then delivers the report or notification to the specified destination. If a report cannot be delivered, an entry is logged to the report server log file. If you want to support retry operations, you can configure the report server to re-attempt the delivery if the first attempt fails.
Processing a Standard Subscription
Standard subscriptions produce one instance of a report. The report is delivered to a single shared folder or to the e-mail addresses specified in the subscription. The report layout and data do not vary. If the report uses parameters, a standard subscription is processed with a single value for each parameter in the report.
Processing a Data-Driven Subscription
Data-driven subscriptions can produce many report instances that are delivered to multiple destinations. The report layout does not vary, but the data in a report can vary if parameter values are passed in from a subscriber result set. Delivery options that affect how the report is rendered and whether the report is attached or linked to the e-mail can also vary from subscriber to subscriber when the values are passed in from the row set.
Data-driven subscriptions can produce a large number of deliveries. The report server creates a delivery for each row in the row set that is returned from the subscription query.
Report Delivery Characteristics
Reports that are delivered through standard subscriptions are typically rendered as static reports. These reports are either based on the most recent report execution snapshot, or generated as a static report for the purpose of completing a delivery. If you choose the Include Link option in a subscription to a report that runs on demand, the report server runs the report when you click the hyperlink.
Reports that are delivered through a URL remain connected to the report server and can be updated or deleted between viewings. The delivery options you choose for your subscription determine whether the report is delivered as a URL, embedded within the body of an e-mail message, or sent as an attachment.
Reports that are delivered through a data-driven subscription may be regenerated while the subscription is being processed. The report server does not lock in a specific instance of a report or its dataset to complete a data-driven subscription. If the subscription uses different parameter values for different subscribers, the report server regenerates the report to produce the required result. If the underlying data is updated after the first report copy is created and delivered, users who get reports later in the process may see data that is based on different result set. You can use a report that runs as a snapshot to ensure that the same report instance is delivered to all subscribers. However, if a scheduled update to the snapshot occurs while the subscription is processing, users may still get different data in their reports.
Triggering Subscription Processing
The report server uses two kinds of events to trigger subscription processing: a time-driven event that is specified in a schedule or a snapshot update event.
A time-driven trigger uses a report-specific schedule or a shared schedule to specify when a subscription runs. For on-demand and cached reports, schedules are the only trigger option.
A snapshot update event uses the scheduled update of a report snapshot to trigger a subscription. You can define a subscription that is triggered whenever the report is updated with new data, based on report execution properties that are set on the report.