Managing Heterogeneous Services Using Generic Connectivity

I'm trying to connect Oracle over ODBC to another database (for testing I use MS SQL Server 7.0).
OS is Windows 200 Professional.

I have checked in SYS schema and there exist needed objects (HS_*).

I have configured listener.ora and tnsnames.ora and restarted listener. I have also created system DSN MSSQL. Checked connection and connection to SQL Server is OK.

Here is what I added in listener.ora:

LISTENER=
      (DESCRIPTION LIST =
(...)

        (ADDRESS_LIST=
            (ADDRESS = (PROTOCOL = ipc )(KEY = PNPKEY))
       )

(...)

SID_LIST_LISTENER =
     (SID_LIST =
   (...)

         (SID_DESC=
              (SID_NAME = MSSQL)
              (ORACLE_HOME = C:\Oracle\Ora81)
              (PROGRAM = hsodbc)
         )
      )

in tnsnames.ora I have, among other things:

mssql = (DESCRIPTION =

                  (ADDRESS = (PROTOCOL=tcp)(HOST=localhost)(PORT=1521))
                  (CONNECT_DATA=(SID=MSSQL))
                   (HS = OK)
               )

I also have initMSSQL.ora file in c:\Oracle\Ora81\hs\admin folder:

HS_FDS_CONNECT_INFO= MSSQL when I try from command prompt:

tnsping mssql

It 'pings' it ok.

But where I create database link, test says 'The Database Link is not active'.
When i try from SQLPLUS something like

select * from table_at_mssql;

I get the message:

database link mssql connects to HO.WORLD. Received on Wed Dec 19 2001 - 14:12:47 CET