APEX Installation ORA-01435 while running @apxconf I'm trying to configure and use APEX on a Oracle Database 12c. When I try to run @apxconf I get the Error ORA-01435. I don't really now what is wrong since I followed the Documentation. https://docs.oracle.com/database/121/HTMIG/E17958-12.pdf#G5.1084317

SQL&gt; @apxconf

PORT
8080

Enter values below for the XDB HTTP listener port and the password for the Appli
cation Express ADMIN user.
Default values are in brackets [ ].
Press Enter to accept the default value.


ERROR:
ORA-01435: Benutzer ist nicht vorhanden.


Verbindung zu Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit
Production beendet


Verbindung zu Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit
Production beendet => Connection closed

Working Directory is dbhome_1/apex.

I'm logged in with sys as sysdba.
Oracle support doc 1970925.1 suggests that this is because you're trying to use the wrong version of script with the installed APEX version (e.g. 5.0 APEX installation but 5.1 scripts).

Ensure you're using the right version of scripts with the right APEX version.

Another reason this could happen, is if APEX isn't even installed.  Note that with 12.2 onwards, APEX isn't installed in the database by default.