What can cause a language key to disappear?

Just noticed that the _adm_page_cpt_manage_modules language key disappeared from my site.  That is a Dolphin language key.  What could just remove it from the system?  I checked, the language key could not be found so I added it back So I could have Manage Modules displayed instead of _adm_page_cpt_manage_modules.

uninstall/reinstall a module. 

I tried to uninstall and reinstall the Forum module and now most of the original lang keys are gone, things cannot be read properly even in English.

Please let me know how to fix it. 

Uninstalling a module should only remove the language keys for that module.  It should not affect system keys.  In my case, it was one key and I simply added it back and entered the text for it.

Using HFW and having them reload your site with an old backup copy...

Maybe I am still confused about how language keys work.  I was told that when you add a language key, it is added to the language key file; not in the database, I was told that by an experience Dolphin developer.

Perhaps we need to discuss how the language keys work so that when we have issues, we can better deal with them.

Nope.

Language keys are added to the database.

For system language keys. The proper method to add a system language key is using the languages section in admin. That adds it to the database. Then when you compile the languages, all keys for all languages including all modules are all combined into language cache files in the langs folder.

For module language keys, the proper way to add them is in the module language file in the modules lang folder. Then you upload that changed file and recompile the modules languages which will import the new keys into the database which in turn gets compiled into the lang cache file in the langs folder. The modules are done differently than the system keys because they get added and removed as the module is installed and uninstalled so they are kept in files, but are still added to the database when the module is installed and removed from the database when the module is uninstalled.

Many people make the mistake of editing the compiled lang file in the langs folder directly which is never to be done. These are the people that you see in the forums that are always complaining that they keep loosing their changes every time they install a module or add a new language or any other change that results in the languages getting recompiled.

Of course, the forums are different which i did not explain, but they have their own language file similar to the modules. And then you recompile the forums.

So in the case of my missing system key; _adm_page_cpt_manage_modules, then it somehow got removed from the database?  I went to languages, and click on the compile button but it did not restore the missing key.  I would like to try to have some understanding of what caused that key to disappeared.  I went to the languages section and searched for it and it was not there; so I added it to restore the title of "Manage Modules".

That is the only explanation. It had to have somehow been removed from the database. If it was removed from the cached copy in the langs folder it would have returned when the languages were compiled, so it had to have been removed from the database.

How is something i cannot tell you. I also cannot tell you what caused it. How about gremlins?

For the forum, I would try to log in as admin, go the forum, click on manage forum, and then click on recompile language for the languages you are using.  Other than that, I don't know.

 
That would be most likely a side effect of not properly maintaining the language keys. If the lang file in the langs folder is edited/modified by hand(which as i mentioned is never to be done) then entries are not in the database as they should be, thus when a module(any module) is installed or uninstalled the languages are recompiled over writing those manual changes with what is currently in the database.

That is my only explanation of the cause.

Can someone please tell me where the language keys are stored in the database? I try to import the system language keys from one Dolphin database to another but I could not find it (the table that keeps all the system language keys).

Thank you

I have found that checking that little box next to a key, then clicking the delete button, causes it to disappear.  That's probably what you did.

 Nope, in my case I just uninstalled the forum, then reinstalled the forum and all the system keys such as 

Go back up and read Deano's explanation of how language keys work.  Your language file could have gotten corrupted.  Install the language file from a good backup; if you don't have a good backup, then you will need to grab it from the Dolphin zip; note you may still see missing language keys.  Then you go to your admin, languages and recompile the language.