Microsoft® SQL Server 2012 Unleashed

How SQL Server Manages Transactions

SQL Server uses the database’s transaction log to record the modifications that occur within the database. Each log record is labeled with a unique log sequence number (LSN), and all log entries that are part of the same transaction are linked together so that they can be easily located if the transaction needs to be undone or redone. The primary responsibility of logging is to ensure transaction durability—either ensuring that the completed changes make it to the physical database files or ensuring that any unfinished transactions are rolled back in the event of an error or a server failure.

What is logged? Obviously, the start and end of a transaction are logged, but SQL Server also logs the actual data ...