March 2003
Intermediate to advanced
912 pages
27h 17m
English
The theory outlined above does not take into account that the operations of a transaction might be undone due to an abort termination. It must be possible to return the system to a consistent state as though the transaction had not taken place. The following problems could arise through concurrent execution of transactions, even if a serializable schedule of suboperations had been devised. It is demonstrated that serializability is necessary but not sufficient for correct concurrent operation.
Figure 19.13 shows a serializable schedule of the transactions T1 and T2 used above in Section 19.7. This time, T1 happens to abort.