Concurrency Control Protocol Research Articles

On predictive modeling for optimizing transaction execution in parallel OLTP systems

A new emerging class of parallel database management systems (DBMS) is designed to take advantage of the partitionable workloads of on-line transaction processing (OLTP) applications [23, 20]. Transactions in these systems are optimized to execute to completion on a single node in a shared-nothing cluster without needing to coordinate with other nodes or use expensive concurrency control measures [18]. But some OLTP applications cannot be partitioned such that all of their transactions execute within a single-partition in this manner. These distributed transactions access data not stored within their local partitions and subsequently require more heavy-weight concurrency control protocols. Further difficulties arise when the transaction's execution properties, such as the number of partitions it may need to access or whether it will abort, are not known beforehand. The DBMS could mitigate these performance issues if it is provided with additional information about transactions. Thus, in this paper we present a Markov model-based approach for automatically selecting which optimizations a DBMS could use, namely (1) more efficient concurrency control schemes, (2) intelligent scheduling, (3) reduced undo logging, and (4) speculative execution. To evaluate our techniques, we implemented our models and integrated them into a parallel, main-memory OLTP DBMS to show that we can improve the performance of applications with diverse workloads.

An Extended Three Phase Commit Protocol for Concurrency Control in Distributed Systems

One of the important issues of distributed system is to improve Concurrency control , I observed that Concurrency Control is very difficult task for distributed systems because of absence of global clock and lack of shared memory. To improve the concurrency control problems in my work, a new modified version of three phase commit protocol is introduced that works for the sake of concurrency control in distributed systems. The basis of this protocol is the division of all the sites into two groups depending upon the number of queries generated and importance of the queries at these sites. The sites where more queries are generated are considered as primary sites and those having less, are considered as secondary sites. The Primary sites are given more importance while deciding whether to commit or abort a transaction. In this a modified version of three phase commit protocol is praposed that ensures if a transaction is originated from a primary site then it is bound to commit provided all other primary sites vote to commit, no matter whether secondary sites commit or not and there the advantages and disadvantages of this new version is considered. It is to be mentioned that this protocol works only for transactions that accesses a single database object. Instances of such transactions could be debiting or crediting a bank account as in this only a single database object such as a personal bank account is accessed.

Modular reasoning for deterministic parallelism

Weaving a concurrency control protocol into a program is difficult and error-prone. One way to alleviate this burden is deterministic parallelism . In this well-studied approach to parallelisation, a sequential program is annotated with sections that can execute concurrently, with automatically injected control constructs used to ensure observable behaviour consistent with the original program. This paper examines the formal specification and verification of these constructs. Our high-level specification defines the conditions necessary for correct execution; these conditions reflect program dependencies necessary to ensure deterministic behaviour. We connect the high-level specification used by clients of the library with the low-level library implementation, to prove that a client's requirements for determinism are enforced. Significantly, we can reason about program and library correctness without breaking abstraction boundaries. To achieve this, we use concurrent abstract predicates , based on separation logic, to encapsulate racy behaviour in the library's implementation. To allow generic specifications of libraries that can be instantiated by client programs, we extend the logic with higher-order parameters and quantification. We show that our high-level specification abstracts the details of deterministic parallelism by verifying two different low-level implementations of the library.

Secure concurrency control protocol with timeliness guarantees in real-time database systems

Real-time database systems (RTDBSs) are usually applied in the time-critical applications with security constraints. For these applications, RTDBSs must simultaneously satisfy two requirements in guaranteeing data security and minimizing the deadline miss ratio for admitted transactions. Multilevel secure database systems based on mandatory access control can prevent direct unlawful information flows between transactions. However, they cannot be free from illegal information transfers between transactions by means of the concurrency control mechanism, so the novel concurrency control algorithms supporting security and real-time requirements are needed for RTDBSs. In this paper, we present a novel secure real-time concurrency control algorithm (SRCC) for RTDBSs. The SRCC makes an effective tradeoff between security constraints and timing constraints by introducing secure control factor and real-time influence factor. Further, in order to obtain the better real-time performance, an enhanced SRCC called ESRCC is proposed by introducing the concept of similarity. The experimental results show that the ESRCC can ensure excellent real-time performance while guaranteeing data security.

Concurrency Control Protocol for Real-Time Database and the Analysis Base on Petri Net

In the article a new concurrency control protocol for real-time database (RTCC) is proposed. The protocol based on the traditional speculative concurrency control protocol (SCC). It dynamically establish the maximum of shadow to reasonably use the resources of system and add the quasi-commit phase to avoid many unnecessary restarting and enhance the concurrency of transaction. The theory of Petri net proof and results of experiment show that this protocol is feasible and effective , and it can meet the needs of real-time transaction. Speculative Concurrency Control is suitable especially for real-time database[1]. On the one hand, SCC is similar to PCC, to detect potentially harmful conflict as early as possible, so as to start a replacement schedule, thereby increasing the opportunities for transactions to meet time limits. On the other hand, SCC is similar to OCC, it allows the concurrency of conflict transaction and, therefore, avoids unnecessary matters that may affect the timely submission of delay. As a result, it alleviates the congestion problems and PCC restart OCC's problems, in order to better meet the transaction deadline. Based on the fact above mentioned, we propose a suitable real-time database concurrency control protocol [2,3] (RTCC: Concurrency Control protocol for Real-Time). The protocol of the SCC protocol on the traditional basis with a series of improvements can avoid a large number of unnecessary transaction restart and improve concurrency. Finally, by Petri net theory it can be proved feasible and correct.

Research and Applications of Access Control Based on Logic SQL Database System

Access control is the process of mediating every request to data and services maintained by a system and determining whether the request should be granted or denied. Access control policies are security policies that govern access to resources. It can be applied to several new types of databases. LogicSQL is an object relational database management system implemented with the advanced (formula-lock based) concurrency control protocol, and the steged database architecture. In this paper, we discuss access control in multilevel database management systems applies and illustrate the main applies of access control in the LogicSQL database system.

A generic simulation model for evaluating concurrency control protocols in native XML database systems

In this paper we propose a generic simulation model, named XSM, with which researchers can construct standard platforms and evaluate their proposed concurrency control protocols for native XDBMSs. The system environment, the performance metrics, and the protocol rules of various types of XML protocols are all considered by the model. To facilitate the implementation of XSM, the state diagrams, the sequence diagrams, the component diagram, and the class diagram of XSM are depicted using UML 2.0 notations. We also show a simulation platform constructed from XSM to fairly and comprehensively evaluate the performance of various XML protocols.

A Multiversion Optimistic Concurrency Control Protocol in Mobile Broadcast Environments

This paper presents MVOCC-MDA-2PV (multiversion optimistic concurrency control with multiversion dynamic adjustment using two-phase validation) protocol for processing mobile real-time transaction in mobile broadcast environments. Transaction validation is performed at two phases: pre-validation and final validation. At the mobile herts (MHs), all mobile transactions (MT) perform pre-validation of transactions by using backward validation mechanism. The pre-validation process is carried out against committed transactions at the server in the last broadcast cycle. Such an early data conflict detection feature can save processing and communication resources. Transactions that survive in pre-validation must be submitted to the server for final validation. The MHs do not need to synchronize with each other and servers for data conflict detection. The protocol can eliminate conflicts between mobile read-only and mobile update transactions, and resolve data conflicts flexibly using multiversion dynamic adjustment of serialization order to avoid unnecessary restarts of transactions. For a mobile ready-only transaction, it can be committed locally in the MH if it passes all the pre-validation in the course of it execution. Respond time of mobile read-only transactions (MROT) is greatly improved. The results of experiment show that the new protocol proposed offers better performance in terms of miss rate and commit rate.

Distributed Management of Concurrent Web Service Transactions

Business processes involve dynamic compositions of interleaved tasks. Therefore, ensuring reliable transactional processing of Web services is crucial for the success of Web service-based B2B and B2C applications. But the inherent autonomy and heterogeneity of Web services render the applicability of conventional ACID transaction models for Web services far from being straightforward. Current Web service transaction models relax the isolation property and rely on compensation mechanisms to ensure atomicity of business transactions in the presence of service failures. However, ensuring consistency in the open and dynamic environment of Web services, where interleaving business transactions enter and exit the system independently, remains an open issue. In this paper, we address this problem and propose an architecture that supports concurrency control on the Web services level. An extension to the standard framework for Web service transactions is proposed to enable detecting and handling transactional dependencies between concurrent business transactions. We also present an optimistic protocol for concurrency control that can be deployed in a fully distributed fashion within the proposed architecture. We also empirically evaluate the performance of the proposed solutions in terms of throughput and response time.

Hypo-Serializable Concurrency Control in Parallel Broadcast Environments

Serializable concurrency control protocols are inapplicable in mobile broadcast environments due to a number of constraints of wireless communications and characteristics of mobile real time applications.In this paper,the use of hypo-serializability for mobile parallel broadcast environments is proposed.At first,hypo-serializability is formally defined.Next,it is proved that hypo-serializability is more relaxing than traditional serializability while consistency is maintained all the time.Then,the necessary and sufficient conditions for hypo-serializability are shown.Furthermore,the parallel hypo-serializable concurrency control protocol BCC-HSR is proposed.Finally,through a series of simulation studies,it is confirmed that the proposed protocol could improve average response time of mobile transactions significantly.

Modeling selected real-time database concurrency control protocols in Uppaal

Real-time database management systems (RTDBMS) are recently subject of an intensive research. Model checking algorithms and verification tools are of great concern as well. In this paper, we show some possibilities of using a verification tool Uppaal on some variants of pessimistic and optimistic concurrency control protocols used in real-time database management systems. We present some possible models of such protocols expressed as nets of timed automata, which are a modeling language of Uppaal.

GLIP: A Concurrency Control Protocol for Clipping Indexing

Multidimensional databases are beginning to be used in a wide range of applications. To meet this fast-growing demand, the R-tree family is being applied to support fast access to multidimensional data, for which the R+-tree exhibits outstanding search performance. In order to support efficient concurrent access in multiuser environments, concurrency control mechanisms for multidimensional indexing have been proposed. However, these mechanisms cannot be directly applied to the R+-tree because an object in the R+-tree may be indexed in multiple leaves. This paper proposes a concurrency control protocol for R-tree variants with object clipping, namely, Granular Locking for clipping indexing (GLIP). GLIP is the first concurrency control approach specifically designed for the R+-tree and its variants, and it supports efficient concurrent operations with serializable isolation, consistency, and deadlock-free. Experimental tests on both real and synthetic data sets validated the effectiveness and efficiency of the proposed concurrent access framework.

A concurrency control scheme for mobile transactions in broadcast disk environments

Broadcast disk technique has been often used to disseminate frequently requested data efficiently to a large volume of mobile clients over wireless channels. In broadcast disk environments, a server often broadcasts different data items with differing frequencies to reflect the skewed data access patterns of mobile clients. Previously proposed concurrency control methods for mobile transactions in wireless broadcast environments are focused on the mobile transactions with uniform data access patterns. These protocols perform poorly in broadcast disk environments where the data access patterns of mobile transactions are skewed. In broadcast disk environments, the time length of a broadcast cycle usually becomes large to reflect the skewed data access patterns. This will often cause read-only transactions to access old data items rather than the latest data items. Furthermore, updating mobile transactions will be frequently aborted and restarted in the final validation stage due to the update conflict of the same data items with high access frequencies. This problem will increase the average response time of the update mobile transactions and waste the uplink communication bandwidth. In this paper, we extend the existing FBOCC concurrency control method to efficiently handle mobile transactions with skewed data access patterns in broadcast disk environments. Our method allows read-only transactions to access the more updated data, and reduces the average response time of updating transactions through early aborts and restarts. Our method also reduces the amount of uplink communication bandwidth for the final validation of the update transactions. We present an in-depth experimental analysis of our method by comparing with existing concurrency control protocols. Our performance analysis shows that it significantly decreases the average response time and the amount of uplink bandwidths over existing methods.

On Analytical Performance Measurement of Concurrency Control Protocols in DBMS

In this paper some commonly used concurrency control protocols have been implemented through simulation. It is well known that the transactions have mainly four properties: atomicity, consistency, isolation and durability, which are known as the ACID properties. The objective of concurrency control is to ensure consistency when a shared database is updated by multiple concurrent transactions. It is also used to increase the database object utilization. Among all the existing concurrency control protocols, standards are locking, two phase locking, graph based protocols, time stamp-based protocol, wait-die scheme and wound-wait scheme. This paper analyze implementation of two phase locking, wait-die and wound-wait schemes. To implement these protocols, a PC based model has been developed first. The outcome of the model is quite satisfactory. The relative performance of those protocols has been compared in terms of utilization. For each protocol a concurrency control manager has been designated which maintains all lock buffers, detects deadlock, and takes necessary action for deadlock recovery. Analyzing the whole experiment it is clear that wait-die scheme and wound-wait scheme protocols show better performance than two phases locking.

Identifying file-sharing P2P traffic based on traffic characteristics

This article focuses on identifying file-sharing peer-to-peer (P2P) (such as BitTorrent (BT)) traffic at the borders of a stub network. By analyzing protocols and traffic of applications, it is found that file-sharing P2P traffic of a single user differs greatly from traditional and other P2P (such as QQ) applications' traffic in the distribution of involved remote hosts and remote ports. Therefore, a method based on discreteness of remote hosts (RHD) and discreteness of remote ports (RPD) is proposed to identify BT-like traffic. This method only relies on flow information of each user host in a stub network, and no packet payload needs to be monitored. At intervals, instant RHD for concurrent transmission control protocol and user datagram protocol flows for each host are calculated respectively through grouping flows by the stub network that the remote host of each flow belongs to. On given conditions, instant RPD are calculated through grouping flows by the remote port to amend instant RHD. Whether a host has been using a BT-like application or not can be deduced from instant RHD or average RHD for a period of time. The proposed method based on traffic characteristics is more suitable for identifying protean file-sharing P2P traffic than content-based methods. Experimental results show that this method is effective with high accuracy.

Scheduling transactions in mobile distributed real-time database systems

A DMVOCC-MVDA (distributed multiversion optimistic concurrency control with multiversion dynamic adjustment) protocol was presented to process mobile distributed real-time transaction in mobile broadcast environments. At the mobile hosts, all transactions perform local pre-validation. The local pre-validation process is carried out against the committed transactions at the server in the last broadcast cycle. Transactions that survive in local pre-validation must be submitted to the server for local final validation. The new protocol eliminates conflicts between mobile read-only and mobile update transactions, and resolves data conflicts flexibly by using multiversion dynamic adjustment of serialization order to avoid unnecessary restarts of transactions. Mobile read-only transactions can be committed with no-blocking, and respond time of mobile read-only transactions is greatly shortened. The tolerance of mobile transactions of disconnections from the broadcast channel is increased. In global validation mobile distributed transactions have to do check to ensure distributed serializability in all participants. The simulation results show that the new concurrency control protocol proposed offers better performance than other protocols in terms of miss rate, restart rate, commit rate. Under high work load (think time is 1s) the miss rate of DMVOCC-MVDA is only 14.6%, is significantly lower than that of other protocols. The restart rate of DMVOCC-MVDA is only 32.3%, showing that DMVOCC-MVDA can effectively reduce the restart rate of mobile transactions. And the commit rate of DMVOCC-MVDA is up to 61.2%, which is obviously higher than that of other protocols.

A self-adaptable scheduler for synchronizing transactions in dynamically configurable environments

In a database system, the scheduler has the goal of synchronizing operations belonging to several concurrent transactions. The scheduler implements a concurrency control protocol, which may have either conservative or aggressive behavior. Existing database systems have schedulers with static behavior. This paper presents a self-adaptable scheduler, called Intelligent Transaction Scheduler (ITS), which has the ability of dynamically changing its behavior to adapt itself to the characteristics of the computing environment, without any human interference by using an expert system based on fuzzy logic. ITS can implement different correctness criteria, such as classical (syntactic) serializability and semantic serializability.

하드와 소프트 실시간 트랜잭션을 위한 통합된 동시성제어 기법

Most concurrency control protocols have been devised for resolving data conflicts among real-time transactions of a single type. Recent real-time database systems should support various types of real-time transactions due to needs of many different types of applications and steady improvement of hardware. In this paper, we propose integrated concurrency control protocol to resolve data conflicts among hard and soft real-time transactions. Our proposed protocol, based on PCP(Priority Ceiling Protocol) for a hard real-time transactions and MVPR(Multiversion with Precedence Relationship), guarantees that hard real-time transactions meet their deadline, and decreases the deadline miss ratio of soft real-time transactions. We also proved that the proposed protocol guarantees serializable schedules and no deadlocks. The performance of the proposed protocol has been compared with other real-time concurrency protocols.

Tolerating byzantine faults in transaction processing systems using commit barrier scheduling

This paper describes the design, implementation, and evaluation of areplication scheme to handle Byzantine faults in transaction processing database systems. The scheme compares answers from queries and updates on multiple replicas which are unmodified, off-the-shelf systems, to provide a single database that is Byzantine fault tolerant. The scheme works when the replicas are homogeneous, but it also allows heterogeneous replication in which replicas come from different vendors. Heterogeneous replicas reduce the impact of bugs and security compromises because they are implemented independently and are thus less likely to suffer correlated failures. The main challenge in designing a replication scheme for transactionprocessing systems is ensuring that the different replicas execute transactions in equivalent serial orders while allowing a high degreeof concurrency. Our scheme meets this goal using a novel concurrency control protocol, commit barrier scheduling (CBS). We have implemented CBS in the context of a replicated SQL database, HRDB(Heterogeneous Replicated DB), which has been tested with unmodified production versions of several commercial and open source databases as replicas. Our experiments show an HRDB configuration that can tolerate one faulty replica has only a modest performance overhead(about 17% for the TPC-C benchmark). HRDB successfully masks several Byzantine faults observed in practice and we have used it to find a new bug in MySQL.

MARK-OPT: A Concurrency Control Protocol for Parallel B-Tree Structures to Reduce the Cost of SMOs

In this paper, we propose a new concurrency control protocol for parallel B-tree structures capable reducing the cost of structure-modification-operation (SMO) compared to the conventional protocols such as ARIES/IM and INC-OPT. We call this protocol the MARK-OPT protocol, since it marks the lowest SMO occurrence point during optimistic latch-coupling operations. The marking reduces middle phases for spreading an X latch and removes needless X latches. In addition, we propose three variations of the MARK-OPT, which focus on tree structure changes from other transactions. Moreover, the proposed protocols are deadlock-free and satisfy the physical consistency requirement for B-trees. These indicate that the proposed protocols are suitable as concurrency control protocols for B-tree structures. To compare the performance of the proposed protocols, the INC-OPT, and the ARIES/IM, we implement these protocols on an autonomous disk system adopting the Fat-Btree structure, a form of parallel B-tree structure. Experimental results in various environments indicate that the proposed protocols always improve system throughput, and 2P-REP-MARK-OPT is the most useful protocol in high update environment. Additionally, to mitigate access skew, data should be migrated between PEs. We also demonstrate that MARK-OPT improves the system throughput under the data migration and reduces the time for data migration to balance load distribution.