The XRay cache is always stored in memory. It can also be stored on disk (i.e. persisted). When also using disk, the entire cache is stored on disk, but only the “hot” items are stored in memory. If it’s required that the current cached info survives CEP restarts, then you would have to enable disk storage as well. This is controlled via the property jkool.track.item.active.persist, which defaults to false. This property can be set in global.properties to true.
What is the path if stored in disk?
The location is controlled via the property fatpipes.data.dir, which defaults to CEP’s home directory (AutoPilotM6/localhost). It can be set to any folder, but should be local storage (e.g. attached disk, or better yet SSD) for optimal performance.
If caching remains in memory, how much RAM is required?
If also persisting, RAM does not have to be large enough to hold everything, but will need to be large enough to hold all events and activities that are being processed.