Information Technology Reference
In-Depth Information
X; an enhanced protocol, obtained by adding some features from
ARIES/KVL
such
as the use of IX locks, is presented by Mohan [
1996a
]. Enhanced key-range locking
protocols for improved concurrency are presented by Lomet [
1993
].
The authors of System R observed that transaction rollback cannot tolerate a
deadlock, implying that it must be able to perform undo actions without acquiring
any new locks [Gray et al.
1981
]. In System R, deadlocks were resolved by selecting
from a cycle of the wait-for graph the youngest transaction whose lock is of short
duration, or just the youngest one if none of the locks in the cycle is of short duration,
and then rolling that transaction back to the savepoint preceding the offending lock
request [Astrahan et al.
1976
]. The need to use conditional lock requests in order to
prevent deadlocks that may arise between latches and locks is discussed by Mohan
[
1990a
,
1996a
], Mohan and Levine [
1992
],andMohanetal.[
1990
,
1992a
].
The classical theory of concurrency control based on the read-write transaction
model is extensively treated in the textbooks by Papadimitriou [
1986
], Bernstein
et al. [
1987
], and Weikum and Vossen [
2002
]. Gray and Reuter [
1993
]presentin
detail how locking is implemented; their textbook also includes a detailed history of
the development of lock-based and other concurrency-control mechanisms.
