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commit protocols FOR EXTERNALIZED-commit HETEROGENEOUS DATABASE-SYSTEMS

DISTRIBUTED AND PARALLEL DATABASES 1994年第2期2卷 209-234页

作者： TAL, A ALONSO, R MATSUSHITA INFORMAT TECHNOL LAB PRINCETONNJ 08540

In designing a heterogeneous database systems, one of the main technical challenges is developing techniques for ensuring global commit. That is, guaranteeing that a transaction spanning multiple individual database management systems (DBMSs) either commits at all the participating DBMSs or at none of them. Previous work in this area typically assumes that the participating DBMSs do not provide a mechanism for interacting with their commit facilities. While this is true in many cases, in practice there are systems which support a programmatic interface to their commit protocols. We refer to database systems offering such facilities as externalized commit DBMSs. The focus of this paper is on commit protocols for these systems. We propose two new commit protocols for externalized commit DBMSs. The first may be used to obtain global commit in heterogeneous database systems composed of DBMSs with different 2-phase commit protocols (e.g., centralized and linear). The second protocol is more general, and ensures global commit even if the participating DBMSs employ 3-phase commit protocols. The more general protocol also preserves database autonomy, since it does not block a DBMS upon failure of another system. We describe both protocols in detail and prove their correctness.

关键词： HETEROGENEOUS DATABASES commit protocols DISTRIBUTED DATABASES AUTONOMY INTEGRATION

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OPEN commit protocols TOLERATING COMMISSION FAILURES

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ACM TRANSACTIONS ON DATABASE SYSTEMS 1993年第2期18卷 289-332页

作者： ROTHERMEL, K PAPPE, S IBM CORP EUROPEAN NETWORKING CTRW-6900 HEIDELBERGGERMANY

To ensure atomicity of transactions in distributed systems so-called 2-phase commit (2PC) protocols have been proposed. The basic assumption of these protocols is that the processing nodes involved in transactions are ''sane,'' i.e., they only fail with omission failures, and nodes eventually recover from failures. Unfortunately, this assumption is not realistic for so-called Open Distributed Systems (ODSs), in which nodes may have totally different reliability characteristics. In ODSs, nodes can be classified into trusted nodes (e.g., a banking server) and nontrusted nodes (e.g., a home PC requesting a remote banking service). While trusted nodes are assumed to be sane, nontrusted nodes may fail permanently and even cause commission failures to occur. In this paper, we propose a family of 2PC protocols that tolerate any number of omission failures at trusted nodes and any number of commission and omission failures at nontrusted nodes. The proposed protocols ensure that (at least) the trusted nodes participating in a transaction eventually terminate the transaction in a consistent manner. Unlike Byzantine commit protocols, our protocols do not incorporate mechanisms for achieving Byzantine agreement, which has advantages in terms of complexity: Our protocols have the same or only a slightly higher message complexity than traditional 2PC protocols.

关键词： ALGORITHMS RELIABILITY commit protocols OPEN SYSTEMS

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THE OVERHEAD OF LOCKING (AND commit) protocols IN DISTRIBUTED DATABASES

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ACM TRANSACTIONS ON DATABASE SYSTEMS 1987年第3期12卷 453-471页

作者： WOLFSON, O The Technion-Israel Institute of Technology Haifa Israel

The main purpose of a locking protocol is to ensure correct interleaving of actions executed by concurrent transactions. The locking protocol consists of a set of rules dictating how accessed entities should be locked and unlocked. As a result of obeying the rules, transactions in a distributed database incur an overhead. We propose three measures of evaluating this overhead, each most suitable to a different type of underlying communication network. Then, using a graph theoretic model, we analyze and compare three protocols according to each measure: two-phase locking, two-phase locking with a fixed order imposed on the database entities (ensuring deadlock freedom), and the tree protocol. In practice, a transaction also executes the two-phase commit protocol in order to guarantee atomicity. Therefore, the combined overhead of each locking protocol and the two-phase commit protocol is also determined.

关键词： commit protocols computer network concurrency control database locking deadlock locking protocols message passing transaction

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EFFICIENT DECENTRALIZED CONSENSUS protocols

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IEEE TRANSACTIONS ON SOFTWARE ENGINEERING 1986年第5期12卷 600-607页

作者： LAKSHMAN, TV AGRAWALA, AK Systems Design and Analysis Group Department of Computer Science University of Maryland College Park MD 20742

Decentralized consensus protocols are described by successive rounds of message interchanges. protocols that achieve a consensus in one round of message interchange need messages of a given set of sites in the system. Here, a communication scheme is presented, based on finite projective plans, which needs only a given set of messages for each round. Employing this communication scheme, decentralized consensus protocols are developed that achieve a consensus within 2 rounds of message interchange. The protocols are symmetric, and the communication plan does not impose any hierarchical structure. The scheme is illustrated using blocking and nonblocking commit protocols, decentralized extrema finding, and computation of the sum function.

关键词： protocols Clocks Checkpointing Concurrent Computing Distributed Databases Computer Science Transaction Management commit protocols Crash Recovery Distributed Database Systems Distributed Systems Fault Tolerance Message Complexity

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OPTIMAL TERMINATION protocols FOR NETWORK PARTITIONING

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SIAM JOURNAL ON COMPUTING 1986年第1期15卷 131-144页

作者： CHIN, F RAMARAO, KVS UNIV PITTSBURGH DEPT COMP SCI PITTSBURGH PA 15260 USA

We address the problem of maintaining the distributed database consistency in presence of failures while maximizing the database availability. Network Partitioning is a failure which partitions the distributed system into a number of parts, no part being able to communicate with any other. Formalizations of various notions in this context are developed and two measures for the performances of protocols in presence of a network partitioning are introduced. A general optimality theory is developed for two classes of protocols—centralized and decentralized. Optimal protocols are produced in all cases.

关键词： commit protocols consistency database availability distributed databases fault-tolerance network partitioning optimal protocols transaction processing

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Atomic commit in concurrent computing

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IEEE CONCURRENCY 2000年第4期8卷 34-41页

作者： Thanisch, P Univ Stirling Alpha Ctr Accrue Software Stirling FK9 4NF Scotland

commit protocols have been proposed for use in a variety of concurrent-computing applications. The author has developed two condition sets that can help you determine when to use a commit protocol and when to avoid them.

关键词： Multiprocessing Programs Multiprocessing Systems protocols Concurrency Control Atomic commit Concurrent Computing commit protocols Condition Sets Concurrent Computing Distributed Databases Transaction Databases Access protocols Database Systems Intelligent Networks File Systems IP Networks Computer Network Management Distributed Computing

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Distributed optimistic concurrency control methods for high-performance transaction processing

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IEEE TRANSACTIONS ON KNOWLEDGE AND DATA ENGINEERING 1998年第1期10卷 173-189页

作者： Thomasian, A IBM Corp Thomas J Watson Res Ctr Hawthorne NY 10532 USA

There is an ever-increasing demand for more complex transactions and higher throughputs in transaction processing systems leading to higher degrees of transaction concurrency and, hence, higher data contention. The conventional two-phase locking (2PL) Concurrency Control (CC) method may, therefore, restrict system throughput to levels inconsistent with the available processing capacity. This is especially a concern in shared-nothing or data-partitioned systems due to the extra latencies for internode communication and a reliable commit protocol. The optimistic CC (OCC) is a possible solution, but currently proposed methods have the disadvantage of repeated transaction restarts. We present a distributed OCC method followed by locking, such that locking is an integral part of distributed validation and two-phase commit. This method ensures at most one re-execution, if the validation for the optimistic phase fails. Deadlocks, which are possible with 2PL, are prevented by preclaiming locks for the second execution phase. This is done in the same order at all nodes. We outline implementation details and compare the performance of the new OCC method with distributed 2PL through a detailed simulation that incorporates queueing effects at the devices of the computer systems, buffer management, concurrency control, and commit processing. It is shown that for higher data contention levels, the hybrid OCC method allows a much higher maximum transaction throughput than distributed 2PL in systems with high processing capacities. In addition to the comparison of CC methods, the simulation study is used to study the effect of varying the number of computer systems with a fixed total processing capacity and the effect of locality of access in each case. We also describe several interesting variants of the proposed OCC method, including methods for handling access variance, i.e., when rerunning a transaction results in accesses to a different set of objects.

关键词： distributed database systems transaction processing optimistic concurrency control access invariance commit protocols system performance modeling

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2-PHASE commit OPTIMIZATIONS IN A COMMERCIAL DISTRIBUTED ENVIRONMENT

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DISTRIBUTED AND PARALLEL DATABASES 1995年第4期3卷 325-360页

作者： SAMARAS, G BRITTON, K CITRON, A MOHAN, C UNIV CYPRUS DEPT COMP SCI NICOSIA CYPRUS IBM CORP ALMADEN RES CTR INST DATABASE TECHNOL SAN JOSE CA 95120 USA

An atomic commit protocol can ensure that all participants in a distributed transaction reach consistent states, whether or not system or network failures occur. The atomic commit protocol used in industry and academia is the well-known two-phase commit (2PC) protocol, which has been the subject of considerable work and technical literature for some years. Much of the literature focuses on improving performance in failure cases by providing a non-blocking 2PC that streamlines recovery processing at the expense of extra processing in the normal case. We focus on improving performance in the normal case based on two assumptions: first, that networks and systems are becoming increasingly reliable, and second, that the need to support high-volume transactions requires a streamlined protocol for the normal case. In this paper, various optimizations are presented and analyzed in terms of reliability, savings in log writes and network traffic, and reduction in resource lock time. The paper's unique contributions include the description of some optimizations not described elsewhere in the literature and a systematic comparison of the optimizations and the environments where they cause the most benefit. Furthermore, it analyzes the feasibility and performance of several optimization combinations, identifying situations where they are effective.

关键词： AGREEMENT protocols DISTRIBUTED SYSTEMS TRANSACTION MANAGEMENT SNA LU 6.2 COMMUNICATION protocols commit protocols RECOVERY FAULT TOLERANCE

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AN EFFICIENT FAULT-TOLERANT DECENTRALIZED commit PROTOCOL

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PARALLEL COMPUTING 1994年第1期20卷 101-114页

作者： YUAN, SM Department of Computer & Information Science National Chiao Tung University Hsinchu 30050 Taiwan

A new efficient decentralized commit protocol is proposed for distributed database systems. This protocol can be applied to systems of all sizes and is [log(2) N] - 2 resilient to site failures, where N is the number of sites in the system. In addition, the number of messages sent among the N sites is (N log(2)(2)N) which is only a factor of log(2) over the message complexity lower bound O(N In N) of decentralized commit protocols.

关键词： commit protocols DECENTRALIZED ALGORITHMS FAULT-TOLERANT ALGORITHMS

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THE COMMUNICATION COMPLEXITY OF ATOMIC commitMENT AND OF GOSSIPING

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SIAM JOURNAL ON COMPUTING 1991年第3期20卷 423-450页

作者： WOLFSON, O SEGALL, A TECHNION ISRAEL INST TECHNOL DEPT COMP SCIIL-32000 HAIFAISRAEL

The problem of atomic commitment of a transaction in a distributed database is considered. This is a variant of the famous gossiping problem. Given a set of communication costs between pairs of participant sites, it is established that the necessary communication cost for any atomic commitment algorithm is twice the cost of a certain minimum spanning tree. This paper establishes the necessary communication time for any atomic commitment algorithm, given a set of communication delays between pairs of participant sites, and the time at which each participant completes its subtransaction. Then, it is determined that both lower bounds are also upper bounds in the following sense. There is an efficient (i.e., polynomial-time) algorithm that, in the absence of failures, has a minimum communication cost. There is another efficient algorithm that, in the absence of failures, has a minimum communication time. However, unless P = NP, there is no efficient algorithm which has a minimum communication complexity, namely, one for which the product of communication cost and communication time is minimum. Next, a simple, linear time, distributed algorithm, called TREE-commit, whose communication complexity is not worse than p times the minimum complexity, where p is the number of participants, is presented. Finally, it is demonstrated that TREE-commit is superior to the existing variants of the two-phase commit protocol.

关键词： commit protocols DATABASE CONSISTENCY DISTRIBUTED DATABASES OPTIMAL protocols TRANSACTION MANAGEMENT GOSSIPING

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