Rollback

Scan backwards from last log record of txn
- (last log record of txn = transTable[TransID].UndoNxtLSN
if log record is an update log record
- undo it and add a CLR to the log
if log record is a CLR
- then UndoNxt = LogRec.UnxoNxtLSN
- else UndoNxt = LogRec.PrevLSN
next record to process is UndoNxt; stop at SaveLSN or beginning of transaction as required

Scan backwards from last log record of txn