Service Event Type: Poll With Step
A Poll With Step service event type references a step definition that is run by SAP Mobile Platform Server periodically to actively poll the source back-end system for data changes. This step definition is commonly a SQL step, though this is not a requirement. The step polling the source back end must return the key property of the object for which the service event has been defined to indicate there is data to be updated to the destination back-end system. When the step returns this value, the service event’s read, data state, and update steps are processed.
This service event type is typically defined when the source back end is a SQL Database system connection, although any back end may be actively polled provided the correct step type definition is used. The only requirement of the step referenced by the service event to poll the source back end is that it return the key property for each object instance of the target object type to be synchronized.
This service event type includes the poll interval, which is the duration of time between polls of the source back end by the service event. The number of objects retrieved from the source back end can be limited to a maximum number of instances per poll interval.
Poll With Step Service Event Attributes
- Name: The internal unique name for the service event definition, must be unique among all service events defined within the same module.
- Step: This attribute references the step definition to be run by the service event to poll the source back end system. The step referenced here should be written to return the key property of the target object type of the service event whenever data has changed in the source back end.
- Object Type: This attribute specifies the target object type of the service event. The properties of this object will store the data retrieved from the source back end to be updated to the destination back end. This may include child object collections where necessary.
- Poll Interval: This attribute specifies the duration of time between polls of the source back end by the service event. This attribute is set in hours, minutes and seconds. The step definition referenced in the Step attribute will be run periodically based on the value in the Poll Interval attribute.
- Object Limit: This attribute specifies the maximum number of object instances to create using the data returned by the service event’s defined step. If this step returns the key property values for objects than specified here, the order in which the step returns them will determine which object instances will be created and which will not.
- Read Steps: This attribute specifies whether to retrieve data from the source back end system using the read steps defined in the service event, or those defined in the target object type of the service event. When this attribute is true, the object’s read steps will be used and the service event’s read steps will not be processed.