Never learnt it at school,and I do not think it is my Textbook. Btw,what did you put for the importance of data integrity.i actually didnt understand what they meant by mirroring in this context... was it mirroring as in RAID or in some other weird TPS way, but rollback is half a tiny little syllabus dot point that for some reason my school really pushed. Like we did it for 3 lessons, and its more of a 10 minute sort of explaination.
Its bascally how if a compoent in the transaction doesnt work, then the whole transaction has to be aborted and returned to the last stable state. its to do with the 'atomnicity' of a system.