How can you tell if the database is down or not?

I am using Spring DefaultMessageListenerContainer to consume messages from a queue. The messages are then stored in the Oracle database.

When the database goes down, I throw the exception from the onMessage method and leave the message in the queue for reprocessing. Below you can see that in DataAccessResourceFailureException and CannotCreateTransactionException, I am throwing the exception from the method that returns it to the queue. Other exceptions do not save the message; they correspond to data objectives, etc.

public void onMessage(javax.jms.Message mqMessage) {
    ...get the message blah, blah, blah
    try {
        this.theService.doMessage(tmaticMessage, theHandler);
    } catch (DataAccessResourceFailureException e) {
        this.slowDown(mqMessage);
        throw e;
    } catch (CannotCreateTransactionException e) {
        this.slowDown(mqMessage);
        throw e;
    } catch (DataAccessException e) {
        ...
    } catch (TmUnusableMessageException e) {
        ...
    } catch (Exception e) {
        ...
    }
}

      

        
        
        
      

    

Reading the Spring docs, I found that a DataAccessResourceFailureException should be thrown "... when the resource completely fails: for example, if we cannot connect to the database using JDBC". The problem is that I just ran the test when I had the DBA took the database and got a new exception: CannotCreateTransactionException. So this is another exception to throw. I am wondering if there are others.

I am using Spring Connections and getHibernateTemplate () to make my calls. Here's the question. How do I know what exceptions can be thrown when the database is down?