Diakrites land wrong in Oracle database Every time we are rolling out a new release same tables are trancated and filled with fresh data. This process is done on a Windows pc with scripts that are run in SqlPlus.

When we do this on our development environment the diakrites are inserted as upsidedown questionmarks (¿) in stead of (ä, ë, ï or ö). 

If the data is insert by hand in PL/SQL Developer the data is inserted in the right way. Because of the great amount of data this is not exceptable to do every time. It is also not possible to do this in the acception and production database.

I have tried to find some solution for this problem on the internet, but cloud not find it.  Is there a solution for this problem?
sqlplus inherits the encoding from calling cmd.exe codepage. You must tell Oracle which codepage is used with NLS_LANG value. Value of NLS_LANG and used codepage have to match. 

Try this:

c:\&gt;chcp 1252
Active code page: 1252

c:\&gt;set NLS_LANG=.WE8MSWIN1252

c:\&gt;sqlplus ...


Note, if you run sql-files then ensure they are saved as "ANSI" (i.e. CP1252 for "Western" Windows). If you use a different encoding then set chcp and NLS_LANG accordingly, for example:

c:\&gt;chcp 65001
Active code page: 65001

c:\&gt;set NLS_LANG=.AL32UTF8

c:\&gt;sqlplus ...


See also https://stackoverflow.com/questions/33783902/odbcconnection-returning-chinese-characters-as/33790600#33790600