====== MTR 4 for Server Admins ======

Learn what you need to know to migrate your Minecraft server towards MTR 4!

===== Migration Steps =====

==== Before migrating ====

  * Some addons like [[mtr_addon:nte:start|Nemo Transit Expansion]] and [[https://modrinth.com/mod/transitmanager|TransitManager]] does not have an MTR 4 version. Please double-check your addon list and evaluate your path before upgrading.
  * MTR 4 requires a Minecraft version of either 1.16.5, 1.17.1, 1.18.2, 1.19.2, 1.19.4, 1.20.1 or 1.20.4. Consider upgrading/downgrading your Minecraft version if you are not using a version listed here.
  * **Make a backup before you attempt to migrate, it's an irreversible process!**

==== Migration ====

MTR 4 automatically migrates datas from MTR 3, and there shouldn't be a lot of steps for the users. In any case, the process is outlined below:

  - Shut down the Minecraft Server, replace the MTR 3 mod jar with MTR 4 in the server's mod directory.
  - Start the server. Note that the first startup may take longer as MTR tries to automatically migrate your MTR 3 data into MTR 4. Subsequent startup should be much faster.
  - After the server has started, you should run the ''/mtr generate'' command to refresh all depot's path and make trains run again.

===== Performance =====

MTR 4 no longer simulates train with the Minecraft Game, but instead runs the simulation in a background thread. This means that MTR 4 now poses much less impact to the tick rate of the server. At the same time, train simulations are not affected by the Minecraft Game's Tick Rate. Please note that this may also result in an increase in CPU usage.

===== Upgrading Minecraft Version =====

While upgrading Minecraft version may seems like a straight forward steps, there are some attention needed, more importantly:

  * Datapacks may break as command syntax changes between Minecraft version
  * When upgrading from 1.16/1.17 to 1.18+, terrain generation will differs, and you will not be able to regenerate your terrain back to it's 1.17 form, even with the use of WorldEdit.
  * When upgrading to 1.20, the font json format has changed. Continue using the old format would cause (i.e. JCM PIDS) to show up as square font.