Gets a unique identifier (GUID) that identifies a specified group of SPWorkItem objects that are most logically processed (for performance) as a contiguous batch. For workflow events, the InstanceId value is used as the BatchId property for their respective work item instances.
Assembly: Microsoft.SharePoint (in Microsoft.SharePoint.dll)
Work items are processed in sort order based on a composite sort key that includes the following properties: Type, DeliveryDate, Site, UserId, WebId, BatchID, and ID.
Because both throttling operations rely on the BatchID property, you must set this property if you intend your ISPWorkItemHost to implement throttling.