Explain why the LSN need not be included in pages stored in the database when physical logging is used together with a cache and log buffer.

What will be an ideal response?

With physical logging the LSN is used to enforce the write-ahead policy and is not used during recovery. Its value lies in determining the relationship between updates to a page after it has been brought into the cache and the corresponding update records in the log. Update records corresponding to updates to the page during its previous stay in the cache must have been moved to mass storage before the page was swapped out. Hence, it is sufficient to associate the LSN with each page in the cache, but it need not be stored in the page. When a page is brought into the cache it is clean and the associated LSN can be initialized to a null value.