ORA-25408: can not safely replay call

Being a "newbie" to Oracle 11g RAC, could someone please provide me with some insight to the error "ORA-25408: can not safely replay call"? Here's the scenario, we're testing a 2 node Oracle 11.1.0.6.0 - 64bit RAC on Windows 2003 64bit edition. While I'm running the following sql script, I shut down the active instance with "shutdown immediate" to simulate TAF which results in the ORA_25408 error. Is this the expected result? Is there any way to avoid this error?

declare val number;

begin

  val := 0;

  WHILE val < 600 LOOP   /* 10 minutes */

    val := Val + 1;

    insert into insert_test (insert_record_id) values (val);

    commit;

    DBMS_LOCK.sleep(1);  /* wait 1 second */