How can I connect to an Oracle database as SYSDBA using dbExpress?

I have a Delphi application that connects to an oracle database.

When I try to log in as SYSDBA, I get the error:

ORA-28009: connection as SYS should be as SYSDBA or SYSOPER

When I try to log in with a user of "SYS AS SYSDBA", I get the error:

ORA-01017: invalid username/password; logon denied

How can I log in as sysdba using a dbExpress connection?

See also this related post regarding ADO

I found nothing specific for special dbexpress driver. But try to add a connection parameter DBA privilege with the value SYSDBA.

Connection.Params.Append('DBA Privilege=SYSDBA'); 

I have no delphi installed to check the concrete syntax of the parameter name. Please try using an underscore instead of the blank.

This page shows several connection strings used in certain tools to connect to oracle database.