In case you are using the DBMS_LDAP package from a reasonable modern environment you may run into the error:
ORA-12703 this character set conversion is not supported
The simple solution to this is to run:
begin
DBMS_LDAP.UTF8_CONVERSION := false;
end;
/
```or if you are using SQL*Plus or SQL Developer, just:
exec DBMS_LDAP.UTF8_CONVERSION := false