At 08:58 PM 18/02/2009, you wrote:

>> Connect with another user name, for example, the database owner.
>>
>> Your customer should be able to supply you with log-in details (at
>> least a name), next, create such a user at your system and you should
>> be able to log in.
>
>I added user with GSEC, but it doesn't work. Complete description of
>my steps is in another reply in this thread :-)

If you decide to do it this way, then you need to include the role SYSDBA in your connection parameters.

./hb