QUESTION:
What is the "DS Request Trace" and what is its purpose for Strategy Distribution Services 9.3.1 and newer?
ANSWER:
Starting in Strategy 9.3.1, additional logging is available for Distribution Services. The "DS Request Trace" is useful when troubleshooting the job(s) that is/are created for a Distribution Services subscription. The trace can be found in the Strategy Diagnostics and Performance Logging tool as shown below.

Note: This trace is not enabled by default. An existing or new "File Log" destination must be selected for this logging to be used.
When a subscription (tied to a schedule) executes or the "Send Now" feature is utilized, a subsequent job is created for Distribution Services.
This trace will display details about this job which was created. When the job runs, a sample of entries logged by the trace are shown below:
Sample Code/Error
2013-12-17 13:47:59.073-05:00 Return S_OK from NCSRequest::Execute(). <Subscription 'Sample Report 10/25/13 1:04:51 PM' (ID = 4ACE2E6C435837A3B74C17B4A21FB89A), Contact 'Administrator' (ID = 54F3D26011D2896560009A8E67019608) >
This trace provides further information for a subscription's execution. The first line provides the subscription name, subscription ID, user name and user ID. The "Schedule Execution ID" entry provides the GUID of the time or event-based schedule whose execution resulted in the execution of the subscription. A "Send Now" or "Send Preview Now" execution will not generate this "Schedule Execution ID".