But why do I get the error on client side BEFORE the server timed out
(the clocks are round 30 secs different)? I know nothing about oracle,
but some lines before I saw

>>> OBK-7043: Sbtwrite: System error
  on 12/18/1998 08:51:54 [ 22186 : brtp ]
>>> OBK-5511: Error in sbtwrite
  on 12/18/1998 08:51:54 [ 22186 : brtp ]

I think this corresponds to the dsierror.log msg.

After these error msg ebu made some sbtremove (you can see various
sessions opened and closed on the server) and finished. I see the timed
out session >after< the sbtremove! So the client got the error >before<
the server timed out???

Roger