The transaction log is the main mechanism used to implement transactions, i.e. the Atomic, Consistent, Isolated, and Durable properties of the common A.C.I.D. definition. By providing a record of changes, AS THEY ARE MADE, the transaction allows rollback (or roll forward) of consistent units of work. This rollback capability is often used independently of recovery, providing a way of backing out unfinished work when an error is encountered. The SQL Server transaction log is an integral part of the system, and as such is much more than typical "log" files, which are more like progress reports or error lists.