Sadly, you can't do it just simply by copying files. You need to transfer your database (or you can not touch it too). How I see how you can move all your data.
First, your data stored at MySQL server in databases: rathena_PRERE_db, rathena_PRERE_log (for pre-renewal mechanic (classic) or rathena_RENEWAL_db, rathena_RENEWAL_log.
First, what needs to do is making a backup of all your databases so even if you will do any mistakes, you will always have the ability to restore from backup.
How to do backup:
Simply, copy all files what you have now somewhere else (open-server), or make an archive of your OpenServer folder (to save your disk space).
Then, you need to back up your databases above. For that you need Run OpenServer -> GreenFlag -> Advanced -> Phpmyadmin (login root, pass empty) (optionally you can always set a password for root if you wish (google how to do that for phpmyadmin, or in settings of phpmyadmin you can always set it)
Now, select database what you want to export, and click on export menu, export method -> quick, and hit "Go" button. And you will download a .sql file of your database
Do it for your databases what you have (prere or for renewal (listed above)).
Save these files somewhere, you will need them (as a backup)
What changed in the 2019 package if compare to 2018 in database?
emulator upgraded to latest version, (all NPCs, all source modifications, all changes, etc up to 12 Feb 2019) (you need this)
also, developers changed some structures of some tables (you need to apply these patches to your current database if you want to just upgrade your database (this is what you're asking)
client files (all of them) like exe, grfs, textures, etc upgraded too (you need this too)
minor many fixes
Files what you need to import to rathena_PRERE_db, or rathena_RENEWAL_db is next:
upgrade_20180830.sql, upgrade_20181010.sql, upgrade_20181220.sql, upgrade_20181224.sql
Files that need to import to rathena_PRERE_log, or rathena_RENEWAL_log:
upgrade_20180729_logs.sql
theory over, now practice, a complete guide on how to upgrade your 2018 package to 2019 with saving all your characters what you have on 2018 package. Step by step guide how to upgrade your 2018 pack to 2019 with saving your characters
1. download the next files:
Extract them somewhere to a new folder, do not overwrite your old files! It's completely different files.
OpenServer you do not need to download, because there are no changes iOpenServerer (except databases) you already have openserver which is exactly the same like in 2018 package (with only one difference, that all rathena databases upgraded).
2. Extract 01_emulator.rar for example to D:\2019\01_emulator
3. Extract 02_clientside.rar for example to D:\2019\02_clientside
4. Now download client kRO client (or if you have already it, you do not need this step)
5. What mechanic do you want to use? Renewal or PRERE? Ask yourself (renewal = new modern content what you see on official servers (dorams, kagero, oboro, sura, and so on), while PRERE it's classical 13.2 episodes (lord knights, high priest, high wizard, clown, etc). For example, I want pre-re. So my steps are next
6. I copy-paste all files from D:\2019\02_clientfiles\FOR_PRERE_EMULATOR\ to my clean kRO client folder.
7. Now, I start my OpenServer what I had earlier from 2018 package. Green Flag. Clicking on it -> Advanced -> PHPMyAdmin -> root, empty pass, enter. Now I'm in phpmyadmin.
8. Now, I select at left: "rathena_PRERE_db", and clicking on it.
9. Now, I click on "import" tab, and I see Import Importing into the database "rathena_PRERE_db", and I see a button "File Import" and button to import sql files, it's looks like next:
10. Now I need import .sql patches to my database from rathena developers 1 by 1 in the same order next files whih stored at D:\2019\01_emulator\rathena_PRERE\sql\upgrades\
I need the next files only (yellow highlighted):
All of these files I 1 by 1 import to my rathena_PRERE_db database with phpmyadmin.
When I have done importing all of these files, now I need to import another one but for rathena_PRERE_log database.
11. I click at phpmyadmin left panel on rathena_RENEWAL_log database, now I click on "Import" tab again, again I see import tab, but now I plan to import only 1 file but to logs database.
I see Import Importing into the database "rathena_PRERE_log" in front of me on display.
And I see File Import Menu, and now I click on "Choose File".
Now again, I need to select ONLY upgrade_20180729_logs.sql and import it to rathena_PRERE_log
I finished the import (this happens in a split second) and now my database is completely updated and I can freely use the updated emulator with the updated client files as well.
As you see it's simple, but require some time.
Now I can safely run:
D:\2019\01_emulator\rathena_PRE\runserver.bat
And my server will work without any errors or problems.
And I will launch a game client which I copy-pasted earlier to clean kRO folder.
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If someone who read the guide use RENEWAL, replace everywhere where you see "PRERE" to RENEWAL and do the same.