This is another follow-up question. In this case, you didn't mention the redo log in your answer. However, instance recovery depends on the redo log. By asking multiple questions about a single topic, the interviewer is indicating that they may have had issues with this in the past and are looking for a candidate who has an in-depth understanding of this topic and can implement it properly if hired. Once you recognize that the interviewer has a specific interest in a topic, you should expand your answers to further demonstrate your knowledge of and qualifications in this area.