CONSTRAINED SHARED LOCKS FOR INCREASING CONCURRENCY IN DATABASES

In this paper, we extend the traditional relationships between locks, i.e., shared and non-shared, to permit sharing in a constrained manner. The new relationship between locks enables us to develop a family of locking protocols, the least permissive of which is two phase locking while the most permissive accepts all order-preserving conflict serializable histories. The latter protocol also accepts all conflict serializable histories without reordering read and write operations. Instances of the family of protocols can cope with a variety of database recovery problems. (C) 1995 Academic Press, Inc.