Buffer Management Policy

• No Force: Only write back to disk when the page needs to be evicted from the buffer pool.
• Steal: Allows modified pages to be written to disk before a transaction finishes.

Write Ahead Logging

Rule:

• Log records must be written to disk before the corresponding data page gets written to disk.
• All log records must be written to disk when a transaction commits.

Implementation:

• LSN: log sequence number.
• Previous LSN: last operation from the same transaction.
• Flushed LSN: the LSN of last log record that has been flushed to disk.
• Page LSN: LSN of the operation that last modified the page.

Recovery Process

• Analysis: reconstruct transaction table, dirty page table.
• Redo: ensure durability.
• Undo: ensure atomicity.