A real-time tracking layer in your map is using a purge rule that could consume a lot of memory and cause poor server performance.
If you are concerned about the real-time tracking layer consuming too much memory in the server, you can change the purge rule of the tracking service that is creating the real-time tracking layer. In the Catalog window, open the General tab of the Tracking Service Properties dialog box for the appropriate tracking service. If you are using the Purge Oldest Records rule, then changing the threshold to a lower number will result in less consumption of server memory. The threshold is the maximum number of features that will be stored in memory at any time.
The purge rule defines how real-time data is stored in system memory. Tracking Analyst stores real-time data completely in memory to maximize performance. To limit the amount of memory consumed, real-time data must occasionally be removed, or purged, from the system memory.