Oracle Instance Architecture - Exercise

This exercise is worth 25 points. Questions 1, 3, and 4 are worth 5 points each; question 2 is worth 10 points.

After submitting, compare your answers with the sample solution and scoring criteria. The website displays your response but does not automatically grade your explanations.

Answer all four questions. Number your responses 1 through 4. You do not need a running database to complete this exercise.

1. Deferred datafile writes — 5 points: Why does Oracle normally modify blocks in the database buffer cache instead of writing every change immediately to its datafile? Explain the performance benefit and Database Writer's role.

2. Commit durability — 10 points: Assume a normal synchronous COMMIT and an instance crash that leaves the database files and online redo logs intact. How can a committed transaction survive even if DBW has not written its changed blocks to datafiles? Explain LGWR, the commit record, redo persistence, and instance recovery.

3. ARCHIVELOG recovery — 5 points: You have a usable database backup from 3:00 a.m. A datafile is lost at noon. How does ARCHIVELOG mode help you recover changes made after the backup? Identify the files required and explain why ARCHIVELOG mode alone does not guarantee recovery to noon.

4. Archiving failure — 5 points: What do ARCn processes do? If required archiving cannot complete because an archive destination is full or unavailable, what can happen when Oracle needs to reuse an online redo log group?

Enter all four numbered answers below, then click Submit.