Soparkar N., Levy E., Korth H.F., Silberschatz A. `Adaptive Commitment for Real-Time Distributed Transactions', Computer Science Department, Technical Report TR-92-15, University of Texas at Austin, 1992.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....configurations. This study would help the Distributed RTDBS designers in making a conscious and more effective decision while choosing the commit protocol for their systems. 4. 9 Related Work on Real Time Commit Protocols The design of real time commit protocols has been investigated earlier in [DLW89, SLKS92, Yoo94, Gup97, HRG99]. DLW89] describes a timed 2PC where the fate of a transaction (commit or abort) is guaranteed to be known to all cohorts of the transaction by the deadline, when there are no processor, communication, or clock faults. In case of faults, however, it is not possible to provide such guarantees, and ....

....we chose to follow this in our work. One more reason for following this model is that, they did not assume any guarantee from the system for the services offered (e.g. messages, data access from the disk, etc. unlike [DLW89] where such guarantees are fundamental to the design of the protocol. [SLKS92, Yoo94] are based on a common theme of allowing individual sites to unilaterally commit the idea is that unilateral commitment results in greater timeliness of actions. If it is later found that the decision is not consistent globally, compensation transactions are used to rectify the errors. While ....

Nandit Soparkar, Eliezer Levy, Henry F. Korth, and Abraham Silberschatz. Adaptive Commitment for Real-Time Distributed Transactions. Technical Re- port TR-92-15, Department of Computer Science, University of Texas-Austin, 1992.

....however, since they arrived at opposing conclusions regarding the utility of adding real time information to buffer management. Research in real time recovery processing has received comparatively less attention than concurrency control. The only papers that we are aware of in this area are [21, 90, 103, 31]. A centralized timed 2PC protocol is described in [21] that guarantees that the fate of a transaction (commit or abort) is known to all the participants of the transaction before the expiry of the deadline, when there are no processor, communication, or clock faults. In case of faults, however, ....

....which indicates the violation of the deadline. Further, the protocol assumes that it is possible for the DRTDBS to guarantee allocation of resources for a duration of time within a given time interval. Moreover, the protocol is predicated upon the knowledge of worst case communication delays. The [90] and [103] papers are based on a common theme of allowing individual sites to unilaterally commit the idea is that unilateral commitment results in greater timeliness of actions. If it is later found that the decision is not consistent globally, compensation transactions are used to rectify ....

N. Soparkar, E. Levy, H. Korth and A. Silberchatz, "Adaptive Commitment for RealTime Distributed Transactions", TR-92-15, Computer Science Department, University of Texas-Austin, 1992.

....course, if an aborting lender has lent to multiple borrowers, then all of them will be aborted, but the abort chain for each borrower is bounded as described above) 8. 5 Related Work on Real Time Commit Protocols The design of real time commit protocols has been investigated earlier in [DLW89, SLKS92, Yoo94, GG94] GG94] addresses the recovery issues in the context of mainmemory real time database systems. DLW89] describes a timed 2PC where the fate of a transaction (commit or abort) is guaranteed to be known to all cohorts of the transaction by the deadline, when there are no processor, ....

....semantics of the transactions as explained in Section 8.1) In addition, we do not assume any guarantees provided by the system for the services offered (e.g. messages, data access from the disk, etc. unlike [DLW89] where such guarantees are fundamental to the design of the protocol. SLKS92, Yoo94] are based on a common theme of allowing individual sites to unilaterally commit the idea is that unilateral commitment results in greater timeliness of actions. If it is later found that the decision is not consistent globally, compensation transactions are used to rectify the ....

Nandit Soparkar, Eliezer Levy, Henry F. Korth, and Abraham Silberschatz. Adaptive Commitment for Real-Time Distributed Transactions. Technical Re- port TR-92-15, Department of Computer Science, University of Texas-Austin, 1992.

....conflict problem has not received adequate attention in the past. Proposals started to appear in the literature only recently. Although several RT CCPs [5, 7, 13, 14, 15, 16] have been proposed, they are mainly for solving the executing executing conflicts. The previous studies are [1, 2, 17, 18]. In [17] and [18] compensation approaches are suggested in which the participants of a transaction are allowed to commit unilaterally, with an attempt to reduce the dependencies amongst the participants of a transaction and to improve the transaction response time. If it is found that the ....

....problem has not received adequate attention in the past. Proposals started to appear in the literature only recently. Although several RT CCPs [5, 7, 13, 14, 15, 16] have been proposed, they are mainly for solving the executing executing conflicts. The previous studies are [1, 2, 17, 18] In [17] and [18] compensation approaches are suggested in which the participants of a transaction are allowed to commit unilaterally, with an attempt to reduce the dependencies amongst the participants of a transaction and to improve the transaction response time. If it is found that the participants ....

Soparkar, N., Levy, E., Korth, H. and Silberschatz, A. (1992) Adaptive commitment for real-time distributed transactions. TR-92-15, Department of Computer Science, University of Texas-Austin.

....conflict problem has not been receiving adequate attention in the past. Proposals started to appear in the literatures only recently. Although several RT CCPs [5, 7, 13, 14, 15, 16] have been proposed, they are mainly for solving the executing executing conflicts. The previous studies are [1, 2, 17, 18]. In [17] and [18] compensation approaches are suggested in which the participants of a transaction are allowed to commit unilaterally with an attempt to reduce the dependencies amongst the participants of a transaction and to improve the transaction response time. If it is found that the ....

....has not been receiving adequate attention in the past. Proposals started to appear in the literatures only recently. Although several RT CCPs [5, 7, 13, 14, 15, 16] have been proposed, they are mainly for solving the executing executing conflicts. The previous studies are [1, 2, 17, 18] In [17] and [18] compensation approaches are suggested in which the participants of a transaction are allowed to commit unilaterally with an attempt to reduce the dependencies amongst the participants of a transaction and to improve the transaction response time. If it is found that the participants ....

Soparkar, N., Levy, E., Korth, H. & Silberschatz, A. (1992) Adaptive Commitment for Real-Time Distributed Transactions. TR-92-15, Department of Computer Science, University of Texas-Austin.

....problematic in the real time context since it has a direct adverse effect on the system s ability to meet transaction timing constraints. Therefore, the choice of commit protocol is an important design decision for DRTDBS. The few papers in the literature that have tried to address this issue [8] [15], 46] have required either relaxing the traditional notion of atomicity or strict resource allocation and resource performance guarantees from the system. Instead of resorting to such fundamental alterations of the standard distributed DBMS framework, we take a different approach in this paper ....

....restarted. HARITSA, RAMAMRITHAM AND GUPTA: THE PROMPT REAL TIME COMMIT PROTOCOL 21 X. Related Work As mentioned in the Introduction, distributed real time commit processing has received little attention in the literature and the only papers that we are aware of dealing with this issue are [8] [15], 46] In this section, we briefly summarize these papers and contrast them with our study. A centralized timed 2PC protocol is described in [8] that guarantees that the fate of a transaction (commit or abort) is known to all the cohorts before the expiry of the deadline when there are no ....

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N. Soparkar et al, "Adaptive Commitment for Real-Time Distributed Transactions," Tech. Rep. TR-92-15, Dept. of Computer Science, Univ. of Texas-Austin, 1992.

....performance) and ecient (makes good use of the lending approach) distributed commit protocol. 14 9. RELATED WORK The material discussed in this chapter is based on our earlier papers [11, 12, 13, 14] Apart from this, the only other work that we are aware of on DRTDBS commit processing is [4, 9, 29]. In this section, we brie y summarize these papers and contrast them with our study. A centralized timed 2PC protocol is described in [4] that guarantees that the fate of a transaction (commit or abort) is known to all the cohorts before the expiry of the deadline when there are no processor, ....

....Note that in a dynamic prioritized system such guarantees are dicult to provide and, further, are generally not recommended since it requires pre allocation of resources, thereby running the risk of priority inversion. A common theme of allowing individual sites to unilaterally commit is used in [9, 29] the idea is that unilateral commitment results in greater timeliness of actions. If it is later found that the decision is not consistent globally, compensation transactions are executed to rectify the errors. While the compensation based approach certainly appears to have the potential to ....

N. Soparkar et al, \Adaptive Commitment for Real-Time Distributed Transactions," Tech. Rep. TR-92-15, Dept. of Computer Science, Univ. of Texas-Austin, 1992.

.... database system and given recent advances in hardware, software and network technology, recently there has been a renewed interest in the search for efficient atomic commit protocols in the context of traditional database systems as well as in emerging ones such as real time database systems [57, 25] and multidatabase systems [13, 37, 66, 4] In this chapter, we have discussed both previous and recent proposals of atomic commit protocols and evaluated the performance of a representative subset of them, both analytically as well as empirically using simulation, providing an insight in the ....

Soparkar N., E. Levy, H. Korth and A. Silberschatz. Adaptive Commitment for Real-time Distributed Transactions. Dept. of Computer Science TR92-15, Univ. of Texas-Austin, 1992.

....a distributed RTDBS is inherently susceptible [6] OPT also incorporates novel features such as Active Abort and Silent Kill that are specifically designed to improve its performance in a real time environment. A special feature of OPT is that it does not, unlike previous efforts in the area [13, 15], require transaction atomicity requirements to be weakened. Our experimental results in [6] showed that, with respect to the metric of the steady state percentage of missed deadlines, OPT provided by far the best performance, primarily due to its optimistic borrowing and active abort policies. ....

N. Soparkar et al, "Adaptive Commitment for Real-Time Distributed Transactions", TR-92-15, CS, Univ. of Texas (Austin), 1992.

....a distributed RTDBS is inherently susceptible [10] OPT also incorporates novel features such as Active Abort and Silent Kill that are specifically designed to improve its performance in a real time environment. A special feature of OPT is that it does not, unlike previous efforts in the area [19, 21], require transaction atomicity requirements to be weakened. Our experimental results in [10] showed that, with respect to the metric of the steady state percentage of missed deadlines, OPT provided by far the best performance, primarily due to its optimistic borrowing and active abort policies. ....

N. Soparkar et al, "Adaptive Commitment for Real-Time Distributed Transactions", TR-92-15, CS, Univ. of Texas (Austin), 1992.

....is described in Section 5, and the results of the simulation experiments are highlighted in Section 6. Finally, in Section 7, we present the conclusions of our study and identify future research avenues. 2 Related Work The design of real time commit protocols has been investigated earlier in [DLW89, SLKS92, Yoo94]. The paper [DLW89] describes a centralized timed two phase commit protocol where the fate of a transaction (commit or abort) is guaranteed to be known to all the participants of the transaction by a deadline, when there are no processor, communication, or clock faults. In case of faults, however, ....

....of the deadline, even at the cost of more transactions eventually being killed. In our work, we focus instead on improving the number of transactions that complete before their deadlines expire, which is of primary concern in the firm deadline application framework (see Section 4. 4) The papers [SLKS92, Yoo94] are based on a common theme of allowing individual sites to unilaterally commit the idea is that unilateral commitment results in greater timeliness of actions. If it is later found that the decision is not consistent globally, compensation transactions are used to rectify the errors. While ....

N. Soparkar, E. Levy, H. Korth and A. Silberschatz, "Adaptive Commitment for Real-Time Distributed Transactions", TR-92-15, Dept. of Computer Science, Univ. of Texas-Austin, 1992.

....needs to access a data item currently held by the borrower. Identifying and handling such deadlocks will impose extra overheads on the system. 7. 3 Protocols Satisfying Relaxed Atomicity through Compensations A radically different approach to improving commit protocol performance is explored in [SLKS92, Yoo94]. 15 Here, individual sites are allowed to unilaterally commit the idea is that unilateral commitment results in improved response times. If it is later found that the decision is not consistent globally, compensation transactions are used to rectify the errors. While the compensation based ....

N. Soparkar, E. Levy, H. Korth and A. Silberschatz, "Adaptive Commitment for Real-Time Distributed Transactions", TR-92-15, CS, Univ. of Texas (Austin), 1992.

....through a graduate student scholarship and National Science Foundation under grants IRI 9210588 and IRI 95020091. and the blocking effects that might lead to the priority inversion problem [8] have been proposed as an alternative to 2PC for the commitment of real time distributed transactions [9, 10]. In these protocols, a participant is allowed to unilaterally commit a real time transaction and release the resources held by the transaction. If the final decision is to abort the transaction, compensation is used to semantically obliterate the effects of the aborted transaction. That is, ....

N. Soparkar, E. Levy, H. Korth and A. Silberschatz, "Adaptive Commitment for Real-Time Distributed Transactions," Technical Report TR-92-15, Department of Computer Science, University of Texas at Austin, 1992.

....database system, we compare the real time performance of a representative set of commit protocols. The performance metric is the steady state percentage of transaction deadlines that are missed. 1.1. Related Work The design of real time commit protocols has been investigated earlier in [17, 19]. These papers are based on a common theme of allowing individual sites to unilaterally commit the idea is that unilateral commitment results in greater timeliness of actions. If it is later found that the decision is not consistent globally, compensation transactions are executed to rectify ....

N. Soparkar, E. Levy, H. Korth and A. Silberschatz, "Adaptive Commitment for Real-Time Distributed Transactions", TR-92-15, CS, Univ. of Texas (Austin), 1992.

....with the requirement that a transaction executes correctly in isolation. Furthermore, it should be clear that a transaction may be regarded as a function that maps consistent states of the database to other consistent states (e.g. see [Pap86, KS88, KLS90] We use this notion of a transaction in [SLKS92] Note that the input predicates are usually derived from the application at hand. Since we use the criterion of serializability for logical correctness, the particulars of the output predicate are not crucial since the execution of a transaction in isolation, by definition, will ensure it. A ....

....abort operation. Note that the use of a compensating transaction means that we can actually 13 defer its execution under certain situations so long as the overall execution appears to have been one where the transaction to be aborted did not execute. We have exploited this technique further in [SLKS92] but we do not discuss the implementation issues that arise with respect to handling immediate aborts and compensations in this paper (see [Sop93] It should be noted that the role of abort operations is much greater in time constrained transaction systems. Even if the underlying system can be ....

[Article contains additional citation context not shown here]

N. R. Soparkar, E. Levy, H. F. Korth, and A. Silberschatz. Adaptive commitment for real-time distributed transactions. Technical Report TR-92-15, The University of Texas at Austin, Computer Sciences Department, April 1992.

....invoked only when required; this reduces the overhead associated with commitment and uses standard correctness criteria during normal operating conditions. There are several issues that are not discussed in this paper mainly due to application specificity and space restrictions; for details see [26]. The decision of the particular point at which one commitment strategy is chosen over another, is one such issue. Also, failures that are essentially catastrophic in an RTDB environment such as a system crash that results in the loss of volatile memory, is another such issue. Furthermore, the ....

N. R. Soparkar, E. Levy, H. F. Korth, and A. Silberschatz. Adaptive commitment for real-time distributed transactions. Technical Report TR-92-15, The University of Texas at Austin, Computer Sciences Department, April 1992.

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Soparkar N., Levy E., Korth H.F., Silberschatz A. `Adaptive Commitment for Real-Time Distributed Transactions', Computer Science Department, Technical Report TR-92-15, University of Texas at Austin, 1992.

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