# Controller replacement - keep history **URL:** \ **Category:** Ignition\ **Created:** [June 7, 2019, 2:04pm UTC](https://forum.inductiveautomation.com/t/controller-replacement-keep-history/25637 "2019-06-07T14:04:39Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![Brian](https://avatars.discourse-cdn.com/v4/letter/b/97f17d/32.png) [@Brian](https://forum.inductiveautomation.com/u/Brian)\ **Post date:** [June 7, 2019, 2:04pm UTC](https://forum.inductiveautomation.com/t/controller-replacement-keep-history/25637/1 "2019-06-07T14:04:39Z")
I’m getting ready to replace a controller on a piece of equipment, and I’m trying to figure out how to retain/reconnect the history recorded from the old controller to the history that will be recorded with the new controller. My old controller is a Honeywell controller, communicating over a serial to ethernet modbus gateway. My new controller is a PLC based controller that will be communicating directly over ethernet using modbus. I have a UDT for the Honeywell controller, and I’m planning on making a new UDT for the PLC. Because the equipment will be doing the same thing, the UDTs will have the same structure. For example, a tag path with history being recorded right now is Draws/Furnace4/Temperature. My tag path with the new UDT will be the exact same thing (I will be removing the old UDT instance). I haven’t replaced controllers like this yet. Does the tag history function work simply based on the tag path? Will everything just start working if I delete the old UDT instance and replace it with a new UDT instance of a different type at the same path? Or, can I just change the existing UDT instance type in place? What’s the best practice for a situation like this? Thanks! ---
**Author:** ![Brian](https://avatars.discourse-cdn.com/v4/letter/b/97f17d/32.png) [@Brian](https://forum.inductiveautomation.com/u/Brian)\ **Post date:** [June 10, 2019, 3:08pm UTC](https://forum.inductiveautomation.com/t/controller-replacement-keep-history/25637/2 "2019-06-10T15:08:36Z")
Bump…