An Efficient Crash Recovery Technique for Real-Time Main Memory Database

This paper presents an efficient recovery scheme suitable for real-time mainmemory database. In the recovery scheme, log records are stored in non-volatile RAM which is dividedinto four different partitions based on transaction types. Similarly, a main memory database isdivided into four partitions based data types. When the using ratio of log store area exceeds thethreshold value, checkpoint procedure is triggered. During executing checkpoint procedure, someuseless log records are deleted. During restart recovery after a crash, partition reloading policyis adopted to assure that critical data are reloaded and restored in advance, so that the databasesystem can be brought up before the entire database is reloaded into main memory. Therefore downtime is obvionsly reduced. Simulation experiments show our recovery scheme obviously improves thesystem performance, and does a favor to meet the dtadlints of real-time transactions.

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 ls） 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.

Validation concurrency control protocol in parallel real-time database systems

In parallel real-time database systems, concurrency control protocols must satisfy time constraints as well as the integrity constraints. The authors present a validation concurrency control(VCC) protocol, which can enhance the performance of real-time concurrency control mechanism by reducing the number of transactions that might miss their deadlines, and compare the performance of validation concurrency control protocol with that of HP2PL(High priority two phase locking) protocol and OCC-TI-WAIT-50(Optimistic concurrency control-time interval-wait-50) protocol under shared-disk architecture by simulation. The simulation results reveal that the protocol the author presented can effectively reduce the number of transactions restarting which might miss their deadlines and performs better than HP2PL and OCC-TI-WAIT-50. It works well when arrival rate of transaction is lesser than threshold. However, due to resource contention the percentage of missing deadline increases sharply when arrival rate is greater than the threshold.

A dynamic crash recovery scheme for distributed real-time database systems

Recovery performance in the event of failures is very important for distributed real-time database systems. This paper presents a time-cognizant logging-based crash recovery scheme （TCLCRS） that aims at distributed real-time databases, which adopts a main memory database as its ground support. In our scheme, each site maintains a real-time log for local transactions and the subtransactions, which execute at the site, and execte local checkpointing independently. Log records are stored in non-volatile high- speed store, which is divided into four different partitions based on transaction classes. During restart recovery after a site crash, partitioned crash recovery strategy is adopted to ensure that the site can be brought up before the entire local secondary database is reloaded in main memory. The partitioned crash recovery strategy not only guarantees the internal consistency to be recovered, but also guarantee the temporal consistency and recovery of the sates of physical world influenced by uncommitted transactions. Combined with two- phase commit protocol, TCLCRS can guarantee failure atomicity of distributed real-time transactions.

Quasi Serializable Concurrency Control in Distributed Real-Time Database Systems

This paper formally defines and analyses the new notion of correctness called quasi serializability, and then outlines corresponding concurrency control protocol QDHP for distributed real-time databases. Finally, through a series of simulation studies, it shows that using the new concurrency control protocol the performance of distributed real-time databases can be much improved.

Real-Time Memory Data Optimization Mechanism of Edge IoT Agent

With the full development of disk-resident databases(DRDB)in recent years,it is widely used in business and transactional applications.In long-term use,some problems of disk databases are gradually exposed.For applications with high real-time requirements,the performance of using disk database is not satisfactory.In the context of the booming development of the Internet of things,domestic real-time databases have also gradually developed.Still,most of them only support the storage,processing,and analysis of data values with fewer data types,which can not fully meet the current industrial process control system data types,complex sources,fast update speed,and other needs.Facing the business needs of efficient data collection and storage of the Internet of things,this paper optimizes the transaction processing efficiency and data storage performance of the memory database,constructs a lightweight real-time memory database transaction processing and data storage model,realizes a lightweight real-time memory database transaction processing and data storage model,and improves the reliability and efficiency of the database.Through simulation,we proved that the cache hit rate of the cache replacement algorithm proposed in this paper is higher than the traditional LRU(Least Recently Used)algorithm.Using the cache replacement algorithm proposed in this paper can improve the performance of the system cache.

A sensor transaction scheduling algorithm for maintaining real-time data temporal validity

A new scheduling algorithm called deferrable scheduling with time slice exchange (DS-EXC) was proposed to maintain the temporal validity of real-time data. In DS-EXC, the time slice exchange method was designed to further defer the release time of transaction instances derived by the deferrable scheduling algorithm (DS-FP). In this way, more CPU time would be left for lower priority transactions and other transactions. In order to minimize the scheduling overhead, an off-line scheme was designed. In particular, the schedule for a transaction set is generated off-line until a repeating pattern is found, and then the pattern is used to construct the schedule on-line. The performance of DS-EXC was evaluated by sets of experiments. The results show that DS-EXC outperforms DS-FP in terms of increasing schedulable ratio. It also provides better performance under mixed workloads.

An Efficient Secure Real-Time Concurrency Control Protocol

Secure real-time databases must simultaneously satisfy two requirements in guaranteeing data security and minimizing the missing deadlines ratio of transactions. However, these two requirements can conflict with each other and achieve one requirement is to sacrifice the other. This paper presents a secure real-time concurrency control protocol based on optimistic method. The concurrency control protocol incorporates security constraints in a real-time optimistic concurrency control protocol and makes a suitable tradeoff between security and real-time requirements by introducing secure influence factor and real-time influence factor. The experimental results show the concurrency control protocol achieves data security without degrading real-time perform ance significantly.

Research on Real-time Data Sharing in Power Integrated Automation System

The Power Integrated Automation System has a large amount of the real-time data, it needs to achieve data sharing in different modules in its own system, sometimes even needs to be shared with the other systems. The thesis discusses the characteristics and the ways of the real-time data sharing in the first place. Then, it compares the merits and drawbacks in different ways. Besides, it gives a viable resolution in different aspects, such as the design of the real-time database, the framework of the communication system and the design of the communication software, as well as the real-time data sharing in different systems.

A Real-time Data Model Based on Temporal Data

Real-time database systems contain not only transaction timing constraints, but also data timing constraints. This paper discusses the temporal characteristics of data in real-time databases and offers a definition of absolute and relative temporal consistency. In real-time database systems, it is often the case that the policies of transaction schedules only consider the deadline of real-time transactions, making it insufficient to ensure temporal correctness of transactions. A policy is given by considering both the deadlines of transactions and the “data deadline” to schedule real-time transactions. A real-time relational data model and a real-time relational algebra based on the characteristics of temporal data are also proposed. In this model, the temporal data has not only corresponding values, but also validity intervals corresponding to the data values. At the same time, this model is able to keep historical data values. When validity interval of a relation is [NOW, NOW], real-time relational algebra will transform to traditional relational algebra.

Research and Application of Synchronization Update of Distributed Heterogeneous Database

According to the different equipment, different system and heterogeneous database have be information ＂isolated island＂ problem, and the data of equipments can be updated in real time on the business node. The paper proposes a program of data synchronization platform based on J2EE （JMS） and XML, and detailed analysis and description of the workflow system, its frame structure and the key technology. Practice shows that this scheme has the advantages of convenient and real-time etc..

The Multi-level Recovery of Main-memory Real-time Database Systems with ECBH

Storing the whole database in the main-memory is a common method to processreal-time transaction in real-time database systems. The recovery mechanism of Main-memory Real-timeDatabase Systems (MMRTDBS) should reflect the characteristics of the main-memory database andreal-time database because their structures are quite different from other conventional databasesystems. In this paper, therefore, we propose a multi-level recovery mechanism for main-memoryreal-time database systems with Extendable Chained Bucket Hashing (ECBH). Owing to the occurrence ofreal-time data in real-time systems, we should also consider it in our recovery mechanism .According to our performance test, this mechanism can improve the transaction concurrency, reducingtransactions ' deadline missing rate.

An IoT-Based Aquaculture Monitoring System Using Firebase

Indonesia is a producer in the fisheries sector,with production reaching 14.8 million tons in 2022.The production potential of the fisheries sector can be optimally optimized through aquaculture management.One of the most important issues in aquaculture management is how to efficiently control the fish pond water conditions.IoT technology can be applied to support a fish pond aquaculture monitoring system,especially for catfish species(Siluriformes),in real-time and remotely.One of the technologies that can provide this convenience is the IoT.The problem of this study is how to integrate IoT devices with Firebase’s cloud data system to provide reliable and precise data,which makes it easy for fish cultivators to monitor fishpond conditions in real time and remotely.The IoT aquaculture fishpond monitoring use 3 parameters:(1)water temperature;(2)pHwater level;and(3)turbidity level of pond water.IoT devices use temperature sensors,pH sensors,and turbidity sensors,which are integrated with a microcontroller and Wi-Fi module.Data from sensor readings are sent to the Firebase cloud via theWi-Fi module so that it can be accessed in real time by end users with an Androidbased mobile app.The findings are(1)the IoT-based aquaculture monitoring system device has a low error rate in measuring temprature,pH,and turbidity with a percentage of 1.75%,1.94% and 9.78%,respectively.Overall,the total average error of the three components is 4.49%;(2)in cost analysis,IoT-based has a cost-effectiveness of 94.21% compared to labor costs.An IoT-based aquaculture monitoring system using Firebase can be effectively used as a technology for monitoring fish pond conditions in real-time and remotely for fish cultivators that contribute to providing an IoT-based aquaculture monitoring system that produces valid data,is precise,is easy to implement,and is a low-cost system.

组态软件中实时数据库系统的设计和实现

文章主要介绍工控组态软件实时数据库系统设计思想，针对实时数据库的特点，提出了一种在Windows环境下，利用动态连接库来建立组态软件实时数据库的方法，给出了数据模型和接口的实现方法，利用该方法建立的实时数据库具有全面的开放性，在实际的应用中证明其数据传递效率大大高于DDE方式。

大型实时数据库系统设计及并发控制调度

系统地分析了大型实时数据库系统的应用环境和功能需求,提出了企业大型实时数据库的体系结构、设计思路和实现方法,研究了实时主动数据库事务执行模式,提出了有效性检查并发控制协议。协议使用动态调整串行次序策略,避免不必要的事务重启动,能有效降低事务延误截止时间,在工程应用中取得了良好的效果。

实时数据库系统关键技术及实现

简要地论述实时数据库的基本概念和特点,分析了实时数据库与传统关系数据库的差异。同时,重点研究了基于Windows平台下实时数据库的实现中关键技术的设计思想和技术路线。根据上述设计思想研制开发的ESP iSYS实时数据库已经在多个工业控制现场得到成功应用。

基于功能替代模型的无冲突并发控制协议

针对周期事务的功能替代模型,支持周期事务的无冲突并发控制协议(SP-CCCP)在CCCP的基础上,增加了新事务与准活跃高优先级周期事务的相容性检测,并改进其与当前活跃事务的相容性检测性能。SP-CCCP选取无冲突的相容替代执行,提高了系统的事务成功率和CPU利用率。仿真实验表明,在资源冲突程度较大的情况下,SP-CCCP的性能优于CCCP。

监控组态软件实时数据库系统体系结构的研究

本文阐述了研究监控组态软件(SCADACS)实时数据库系统(RTDBS)的必要性,概述了通用RTDBS的功能和特点。然后根据监控组态软件中的RTDBS的功能和特点提出了一种监控组态软件中的RTDBS的体系结构,并探讨其体系结构中的组成部分:组态数据库,事件库,优先级库及事务调度,历史数据缓冲机制,主动机制,内存数据库.实时运行系统,并给出其参考实现模型。最后给出该RTDBS的实验性能指标。

基于操作系统的实时数据库移植

介绍了实时数据库的基本概念和主要技术，讨论了实时数据库移植到不同操作系统的方法，结合由美国维吉尼亚大学开发的Starbase实时数据库，实现了实时数据库从操作系统RT-Mach到Unix的移植。

基于组态软件的煤炭企业实时数据库设计

介绍了实时数据库系统的设计思想和实现方法,给出了实时数据库接口的实现方法。实验证明应用高性能实时数据库组件可以大大提高煤炭工业控制系统集成的性能。