Speed up cancellation signal to Oracle

Question

When I cancel my Task using CancellationToken method, It usually get's cancelled around min. 30 seconds. Time depends on how heavy query in Oracle is, it can take even to 1 minute.

Task is called on different thread, using Task.Run (doing some UI loading animations while fetching data) .

If user cancels Task (closes window) while running and starts some new Oracle Task in app, things get's messed up - suddenly a lot of opened sessions appear in Oracle. I want avoid that by speeding up cancellation signal.

Here is my code:

    //global static variable, defined when window opens
    CancellationTokenSource cts= new  CancellationTokenSource(); 
    
    //CancellationToken get's cancelled when user leaves window
    private void OnCloseWindow(object target, ExecutedRoutedEventArgs e)
    {
         cts.Cancel(); 
    }
    
    public async Task<List<EmployeeModel>> Get_Employees(CancellationToken cts)
    {
      var data = new List<EmployeeModel>();
        
      try
      {
        using (OracleConnection con = new OracleConnection(conn_string))
        {
           con.OpenAsync(cts);
        
           OracleCommand cmd = new OacleCommand("Myschema.Procedure_1", con)
           {
             CommandType = CommandType.StoredProcedure
           };
           cmd.Parameters.Add("name_in", OracleDbType.Varchar2).Value = "John";
           cmd.Parameters.Add("surname_in", OracleDbType.Varchar2).Value = "Black";
                       
           using (cts.Register(() => cmd.Cancel()))
           {            
             using (OracleDataReader rdr = cmd.ExecuteReaderAsync(cts))
             {
               while (await rdr.ReadAsync(cts))
               {  
                 data.Add(new EmployeeModel()
                 {
                   NAME = rdr.IsDBNull(0) ? null : rdr.GetString(0),
                   SURNAME = rdr.IsDBNull(1) ? null : rdr.GetString(1)
                 });
               }
             }
           }
         }
      }
      return data;
      }
      catch (OperationCanceledException)
      {
        return null;
      }
      catch (Exception)
      {
        return null;
      }
   }

I'm using OracleManagedDataAccess.dll, version 4.122.19.1. My workaround is to use setting on connection string for Max pool size=3. That - at least during testing - doesn't produce more than 3 sessions at once in Oracle, but I'm not sure if this is the right way.

Is there anything else I can do to fasten cancellation to Oracle? Some kind of mechanism that I'm not aware of?