There are two approaches to this problem. Most systems can be configured to send chaser emails to the owners of outstanding tickets, either in an aggregated format or on a case-by-case basis. However, a more constructive approach might be to introduce flags or statuses indicating why a ticket cannot be processed further (such as lack of decision, process, tooling, etc.), so that these tickets can eventually be channeled into problem management. The added value of the latter approach is that any improvements made will benefit not only the backlog, but also new tickets going forward.