System for selectively registering and blocking requests initiat

Details System for selectively registering and blocking requests initiat System for selectively registering and blocking requests initiat

1991-02-21

1993-11-16

Lee, Thomas C.

Boots, shoes, and leggings

3642814, 3642821, 3642834, 364DIG1, 3642815, 395650, G06F 900

Patent

active

052631559

ABSTRACT:
A method is disclosed for concurrency control in a system having both pessimistic and optimistic transactions, comprises the steps of entering locks on objects both for optimistic and pessimistic transactions, and validating an optimistic transaction at commit time by checking that all objects on which said optimistic transaction holds a lock have not become obsolete during the execution of said optimistic transaction. Further, a system is shown enabling optimistic and pessimistic transactions to coexist, comprising a lock table into which locks are entered for both optimistic and pessimistic transactions, a wait queue in which pessimistic transactions are entered to wait for locks held by either optimistic or pessimistic transactions, a conflict table which is referenced to determine if a lock held by a first transaction is a conflict lock with respect to a lock requested by a second transaction, and code connected to the lock table, wait queue, and conflict table. This code which is responsive to transaction requests, updates the lock table and the wait queue so that optimistic transactions do not wait for locks to release, whereas pessimistic transactions do wait for locks to release. Other systems and methods are also disclosed.

REFERENCES:
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Date, C. J., An Introduction To Database Systems, Addison-Wesley Publishing Company, 1986, pp. 422-427.
Penney, Jason D. et al., "Is The Disk Half Full or Half Empty?", Workshop on Persistent Object Systems, Appin, Scotland, 1987.
Penney, Jason D. et al., Is the Disk Half Full or Half Empty? Combining Optimistic and pessimistic Concurrency Mechanisms in a Shared, Persistent Object Base (Abstract), Appeared: Workshop on Persistent Object Systems, Appin, Scotland, Aug., 1987, pp. 1-18,
Maurice P. Herlihy, et al., Hybrid Concurrency Control For Abstract Data Types (Extended Abstract-Dec. 2, 1987), Appeared: ACM Symposium on Principals Offer Database Systems, 1988, pp. 1-25.
Wang, Chung C., A Strawman Reference Model in Transaction Processing for an Object Oriented Database (Abstract), Appeared: OODBTG Workshop, Oct. 23, 1990, Ottawa, Canda, Created in Information Technologies Laboratory, Technical Report 90-08-xx, Computer Science Center, Texas Instruments, Incorporated, P.O. Box 655474, MS 238, Dallas, Tex. 75265, pp. 1-10.
Andrews, Tim, et al., The Ontos Object Database (Technical Report), by Ontologic, Inc., Three Burlington Woods, Burlington, Mass. 01803, Oct., 1989, pp. 1-22.
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