
376 ◾ Appendix B
a transaction but not make any changes to the database. Only if a transaction com-
mits should the database be updated. is means that the log files have to be kept
in stable storage. Various modifications to the above techniques have been proposed
to handle the different situations.
When transactions are executed at multiple data sources, then a protocol called
two-phase commit is used to ensure that the multiple data sources are consistent.
Figure B.5 illustrates the various aspects of transaction management.
B.2.3.3 Storage Management
e storage manager is responsible for accessing the database. To improve the
efficiency of query ...