By default, Splunk AppDynamics retains transaction snapshots that it captures at regular intervals and when a transaction is detected to be performing abnormally. The snapshots may have full, partial, or no call graphs. See Troubleshoot Business Transaction Performance with Transaction Snapshots.

Diagnostic sessions let you trigger a timed session in which Splunk AppDynamics captures transaction snapshots for a business transaction at a more frequent interval that you set. In the session, Splunk AppDynamics captures full call graphs for the transactions.

Diagnostics sessions can also be triggered automatically by a health rule violation or in response to an abnormal amount of slow or error transactions. By default, if more than 10% of the requests in a minute are slow, Splunk AppDynamics starts a diagnostic session.

If the diagnostic session is triggered manually, the diagnostic session collects snapshots on all the nodes that the selected business transaction passes through. If the diagnostic session is triggered to start automatically, the diagnostics session collects snapshots on the triggering node.