What is the purpose of the recovery log in a database system?

What is the purpose of the recovery log in a database system?

• A. Indicates a point in the recovery log when updates are written to disk
• B. Causes updates to be written directly to disk without logging
• C. Stores historical query results for faster access
• D. Logs database updates and ensures against loss of updates

Answer: (D)

The recovery log is used to ensure durability and crash recovery by recording every database update before it’s applied to the data files (a write-ahead mechanism). By keeping a durable, sequential record of changes, the system can replay or undo operations after a crash, bringing the database back to a consistent state and preventing loss of updates. This is why the purpose is best described as logging updates and protecting against loss of those updates. Other options don’t fit this purpose: a log isn’t mainly a timing indicator for when updates hit disk, nor is it about bypassing logging to write directly to disk, and it isn’t a store of historical query results for faster access.

The recovery log is used to ensure durability and crash recovery by recording every database update before it’s applied to the data files (a write-ahead mechanism). By keeping a durable, sequential record of changes, the system can replay or undo operations after a crash, bringing the database back to a consistent state and preventing loss of updates. This is why the purpose is best described as logging updates and protecting against loss of those updates.

Other options don’t fit this purpose: a log isn’t mainly a timing indicator for when updates hit disk, nor is it about bypassing logging to write directly to disk, and it isn’t a store of historical query results for faster access.