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Lock Conversion in Non-Two-Phase Locking Protocols
January 1985 (vol. 11 no. 1)
pp. 15-22
C. Mohan, IBM Research Laboratory
A locking protocol is a set of rules governing the manner in which the database entities may be accessed. Such a protocol usually employs several kinds of locks. Most of the previous work in this area has assumed that once a transaction acquires a particular kind of lock on a data item it is not allowed to convert this lock to another kind. In this paper we perform a systematic study of the consequences of allowing lock conversions in non-two-phase locking protocols, and show how this leads to increased concurrency and affects deadlock-freedom. The non-two-phase protocols that we study are the very general guard protocols defined for databases in which a directed acyclic graph structure can be superimposed on the data items. We present very natural generalizations of these protocols, including correctness proofs, and develop deadlock removal methods.
Index Terms:
transactions, Concurrency, consistency, database systems, deadlocks, locking protocols, rollbacks, serializability
C. Mohan, D. Fussell, Z.M. Kedem, A. Silberschatz, "Lock Conversion in Non-Two-Phase Locking Protocols," IEEE Transactions on Software Engineering, vol. 11, no. 1, pp. 15-22, Jan. 1985, doi:10.1109/TSE.1985.231533
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