1) run server with following code:

procedure TMainForm.ServerEngineBeforeInsertUpdateTrigger(Sender: TObject;
  TriggerSession: TDBISAMSession; TriggerDatabase: TDBISAMDatabase;
  const TableName: String; CurrentRecord: TDBISAMRecord);
  var ParamsParamGUID, ParamsBizonSearch,
      ParamsParamName, ParamsParamBody, ParamsParamDisplayBody: TField;
begin
  ParamsParamGUID   := CurrentRecord.FieldByName('ParamGUID');
  ParamsBizonSearch := CurrentRecord.FieldByName('BizonSearch');
  ParamsParamName   := CurrentRecord.FieldByName('ParamName');
  ParamsParamBody   := CurrentRecord.FieldByName('ParamBody');
  ParamsParamDisplayBody := CurrentRecord.FieldByName('ParamDisplayBody');
  if ParamsParamGUID.IsNull or (Trim(ParamsParamGUID.AsString) = '') then
    ParamsParamGUID.AsString := CreateClassID;
  ParamsParamDisplayBody.AsString := ParamsParamBody.AsString;
  ParamsBizonSearch.AsString := ParamsParamGUID.AsString + '=' + ParamsParamName.AsString;
end;

2) run DBSYS (default login and password)
3) open table Params
4) insert new record and put xx to ParamName field
5) post record
6) duplicate key error should be raised
7) re-post record without changing
8) #10030 error should be raised