DOCSLIB.ORG

Transactions and Data Management in Nosql Cloud Databases

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Transactions and Data Management in Nosql Cloud Databases Transactions and Data Management in NoSQL Cloud Databases Adewole Conrad Ogunyadeka November, 2016 Department of Computing and Communications Technologies Faculty of Technology, Design and Environment Oxford Brookes University Oxford Brookes University A dissertation submitted to the Faculty of Technology, Design and Environment in partial fulfilment of the requirements of the award of Doctor of Philosophy. Abstract NoSQL databases have become the preferred option for storing and processing data in cloud computing as they are capable of providing high data availability, scalability and efficiency. But in order to achieve these attributes, NoSQL databases make certain trade-offs. First, NoSQL databases cannot guarantee strong consistency of data. They only guarantee a weaker consistency which is based on eventual consistency model. Second, NoSQL databases adopt a simple data model which makes it easy for data to be scaled across multiple nodes. Third, NoSQL databases do not support table joins and referential integrity which by implication, means they cannot implement complex queries. The combination of these factors implies that NoSQL databases cannot support transactions. Motivated by these crucial issues this thesis investigates into the transactions and data management in NoSQL databases. It presents a novel approach that implements transactional support for NoSQL databases in order to ensure stronger data consistency and provide appropriate level of performance. The novelty lies in the design of a Multi- Key transaction model that guarantees the standard properties of transactions in order to ensure stronger consistency and integrity of data. The model is implemented in a novel loosely-coupled architecture that separates the implementation of transactional logic from the underlying data thus ensuring transparency and abstraction in cloud and NoSQL databases. The proposed approach is validated through the development of a prototype system using real MongoDB system. An extended version of the standard Yahoo! Cloud Services Benchmark (YCSB) has been used in order to test and evaluate the proposed approach. Various experiments have been conducted and sets of results have been generated. The results show that the proposed approach meets the research objectives. It maintains stronger consistency of cloud data as well as appropriate level of reliability and performance. Declaration Declaration Some parts of the work presented in this thesis have previously appeared in the following published paper: Ogunyadeka A, Younas M, Zhu H, Aldea A. “A Multi-Key Transactions Model for NoSQL Cloud Database Systems”, Proc. of the 2nd IEEE International Conference on Big Data Computing Service and Applications (BigDataService 2016), Oxford, England, UK, 29 March -1 April 2016. ii Acknowledgements Acknowledgements I would like to express my deepest gratitude and appreciation to my supervisor and Director of Studies Dr. Muhammad Younas, for his exceptional leadership, patience and mentoring. His guidance and support was unwavering throughout the period of this thesis. I could not have wished for a better supervisor. I would also like to thank my co-supervisors Dr Arantza Aldea and Professor Hong Zhu, for their support, encouragement and insightful comments in the period of this research. I am truly grateful for such a wonderful team. I will also like to thank my church family, members of Holding Forth the Word Ministry, Milton Keynes and in particular Revd. Biyi Ajala, for his support during the period of this study. I will also like to appreciate my first boss, Mr Isaac Orolugbagbe, for his support and for encouraging me to aim higher. Also, my appreciation goes to my family members who have stayed by me the last few years and to my brothers Soji, Gbolahan and Bolaji. I will particularly like to thank my father Mr Ayo Ogunyadeka for his immense support and also for bearing the entire financial burden of this research. Finally, I will like to thank my wife Ibijoke for her patience and understanding during this period and to my wonderful son, Olufemi. God bless you both. To God be all the Glory, great things He has done, greater things He will do! iii TABLE OF CONTENTS TABLE OF CONTENTS Abstract ............................................................................................................ i Declaration ...................................................................................................... ii Acknowledgements ......................................................................................... iii TABLE OF CONTENTS ....................................................................................... iv LIST OF FIGURES .............................................................................................viii LIST OF TABLES ................................................................................................. x LIST OF ABBREVIATIONS .................................................................................. xi CHAPTER 1 ....................................................................................................... 1 INTRODUCTION ................................................................................................ 1 1.1 CLOUD COMPUTING .......................................................................... 2 1.2 NoSQL DATABASES and TRANSACTIONS ............................................. 3 1.3 MOTIVATION AND RATIONALE OF THE RESEARCH .............................. 5 1.3.1 Statement of the Research Problem ................................................. 5 1.4 AIM and OBJECTIVES ......................................................................... 6 1.5 RESEARCH METHODS ......................................................................... 7 1.6 MAIN CONTRIBUTIONS ...................................................................... 8 1.7 STRUCTURE OF THE THESIS ................................................................ 9 CHAPTER 2 ..................................................................................................... 11 BACKGROUND ............................................................................................... 11 2.1 DATABASE MANAGEMENT SYSTEMS ................................................ 11 2.2 DATABASE TRANSACTION MANAGEMENT........................................ 12 2.2.1 ACID Properties ............................................................................... 13 2.2.2 Serializability ................................................................................... 15 2.2.3 Concurrency Control Techniques .................................................... 16 2.3 DISTRIBUTED TRANSACTION MANAGEMENT .................................... 17 2.4 TRANSACTION RECOVERY PROTOCOLS ............................................. 19 2.4.1 Two Phase Commit ......................................................................... 19 2.5 BIG DATA and NoSQL DATABASES .................................................... 24 2.6 BIG DATA MANAGEMENT IN NOSQL DATABASES ............................. 25 iv TABLE OF CONTENTS 2.6.1 Partitioning ...................................................................................... 25 2.6.2 Scaling ............................................................................................. 26 2.6.3 Replication ...................................................................................... 27 2.6.4 Failure Detection and Recovery ...................................................... 28 2.6.5 Load Balancing ................................................................................ 28 2.6.6 Garbage collection .......................................................................... 29 2.7 ANALYSIS OF CAP THEOREM ............................................................ 29 2.7.1 BASE ................................................................................................ 32 2.7.2 Other Consistency Models .............................................................. 34 2.8 SUMMARY ...................................................................................... 34 CHAPTER 3 ..................................................................................................... 36 DATA PROCESSING IN CLOUD COMPUTING ..................................................... 36 3.1 ACHITECTURAL CONSIDERATIONS of CLOUD DATABASES ................. 37 3.1.1 Loose Coupling VS Tight Coupling ................................................... 37 3.1.2 Share Nothing VS Shared Disk ......................................................... 38 3.1.3 Data Model...................................................................................... 38 3.1.4 Concurrency Control Techniques .................................................... 39 3.1.5 Replication ...................................................................................... 39 3.1.6 Master-Slave VS Peer to Peer Architecture .................................... 40 3.1.7 Query Processing Approach ............................................................ 40 3.1.8 Read Optimised VS Write Optimised .............................................. 41 3.1.9 Latency VS Durability ...................................................................... 42 3.2 NOSQL DATABASES AND BIG DATA .................................................. 42 3.2.1 BIGTABLE ......................................................................................... 44 3.2.2 MONGODB .....................................................................................
Load more

Recommended publications
  • Rainblock: Faster Transaction Processing in Public Blockchains
    RainBlock: Faster Transaction Processing in Public Blockchains Soujanya Ponnapalli1, Aashaka Shah1, Souvik Banerjee1, Dahlia Malkhi2, Amy Tai3, Vijay Chidambaram1,3, and Michael Wei3 1University of Texas at Austin, 2Diem Association and Novi Financial, 3VMware Research Abstract Metric No state State: 10M Ratio We present RAINBLOCK, a public blockchain that achieves Time taken to mine txs (s) 1047 6340 6× " high transaction throughput without modifying the proof-of- # Txs per block 2150 833 2.5× # work consensus. The chief insight behind RAINBLOCK is that Tx throughput (txs/s) 28.6 4.7 6× # while consensus controls the rate at which new blocks are added to the blockchain, the number of transactions in each Table 1: Impact of system state on blockchain throughput. block is limited by I/O bottlenecks. Public blockchains like This table shows the throughput of Ethereum with proof-of- Ethereum keep the number of transactions in each block low work consensus when 30K txs are mined using three miners, so that all participating servers (miners) have enough time to in two scenarios: first, there are no accounts on the blockchain, process a block before the next block is created. By removing and in the second, 10M accounts have been added. Despite the I/O bottlenecks in transaction processing, RAINBLOCK al- no other difference, tx throughput is 6× lower in the second lows miners to process more transactions in the same amount scenario; we trace this to the I/O involved in processing txs. of time. RAINBLOCK makes two novel contributions: the RAIN- BLOCK architecture that removes I/O from the critical path of processing transactions (txs), and the distributed, multi- Bitcoin [1] and Ethereum, process only tens of transactions versioned DSM-TREE data structure that stores the system per second, limiting their applications [33, 65].
    [Show full text]
  • Big Data Velocity in Plain English
    Big Data Velocity in Plain English John Ryan Data Warehouse Solution Architect Table of Contents The Requirement . 1 What’s the Problem? . .. 2 Components Needed . 3 Data Capture . 3 Transformation . 3 Storage and Analytics . 4 The Traditional Solution . 6 The NewSQL Based Solution . 7 NewSQL Advantage . 9 Thank You. 10 About the Author . 10 ii The Requirement The assumed requirement is the ability to capture, transform and analyse data at potentially massive velocity in real time. This involves capturing data from millions of customers or electronic sensors, and transforming and storing the results for real time analysis on dashboards. The solution must minimise latency — the delay between a real world event and it’s impact upon a dashboard, to under a second. Typical applications include: • Monitoring Machine Sensors: Using embedded sensors in industrial machines or vehicles — typically referred to as The Internet of Things (IoT) . For example Progressive Insurance use real time speed and vehicle braking data to help classify accident risk and deliver appropriate discounts. Similar technology is used by logistics giant FedEx which uses SenseAware technology to provide near real-time parcel tracking. • Fraud Detection: To assess the risk of credit card fraud prior to authorising or declining the transaction. This can be based upon a simple report of a lost or stolen card, or more likely, an analysis of aggregate spending behaviour, aligned with machine learning techniques. • Clickstream Analysis: Producing real time analysis of user web site clicks to dynamically deliver pages, recommended products or services, or deliver individually targeted advertising. Big Data: Velocity in Plain English eBook 1 What’s the Problem? The primary challenge for real time systems architects is the potentially massive throughput required which could exceed a million transactions per second.
    [Show full text]
  • Let's Talk About Storage & Recovery Methods for Non-Volatile Memory
    Let’s Talk About Storage & Recovery Methods for Non-Volatile Memory Database Systems Joy Arulraj Andrew Pavlo Subramanya R. Dulloor [email protected] [email protected] [email protected] Carnegie Mellon University Carnegie Mellon University Intel Labs ABSTRACT of power, the DBMS must write that data to a non-volatile device, The advent of non-volatile memory (NVM) will fundamentally such as a SSD or HDD. Such devices only support slow, bulk data change the dichotomy between memory and durable storage in transfers as blocks. Contrast this with volatile DRAM, where a database management systems (DBMSs). These new NVM devices DBMS can quickly read and write a single byte from these devices, are almost as fast as DRAM, but all writes to it are potentially but all data is lost once power is lost. persistent even after power loss. Existing DBMSs are unable to take In addition, there are inherent physical limitations that prevent full advantage of this technology because their internal architectures DRAM from scaling to capacities beyond today’s levels [46]. Using are predicated on the assumption that memory is volatile. With a large amount of DRAM also consumes a lot of energy since it NVM, many of the components of legacy DBMSs are unnecessary requires periodic refreshing to preserve data even if it is not actively and will degrade the performance of data intensive applications. used. Studies have shown that DRAM consumes about 40% of the To better understand these issues, we implemented three engines overall power consumed by a server [42]. in a modular DBMS testbed that are based on different storage Although flash-based SSDs have better storage capacities and use management architectures: (1) in-place updates, (2) copy-on-write less energy than DRAM, they have other issues that make them less updates, and (3) log-structured updates.
    [Show full text]
  • Not ACID, Not BASE, but SALT a Transaction Processing Perspective on Blockchains
    Not ACID, not BASE, but SALT A Transaction Processing Perspective on Blockchains Stefan Tai, Jacob Eberhardt and Markus Klems Information Systems Engineering, Technische Universitat¨ Berlin fst, je, [email protected] Keywords: SALT, blockchain, decentralized, ACID, BASE, transaction processing Abstract: Traditional ACID transactions, typically supported by relational database management systems, emphasize database consistency. BASE provides a model that trades some consistency for availability, and is typically favored by cloud systems and NoSQL data stores. With the increasing popularity of blockchain technology, another alternative to both ACID and BASE is introduced: SALT. In this keynote paper, we present SALT as a model to explain blockchains and their use in application architecture. We take both, a transaction and a transaction processing systems perspective on the SALT model. From a transactions perspective, SALT is about Sequential, Agreed-on, Ledgered, and Tamper-resistant transaction processing. From a systems perspec- tive, SALT is about decentralized transaction processing systems being Symmetric, Admin-free, Ledgered and Time-consensual. We discuss the importance of these dual perspectives, both, when comparing SALT with ACID and BASE, and when engineering blockchain-based applications. We expect the next-generation of decentralized transactional applications to leverage combinations of all three transaction models. 1 INTRODUCTION against. Using the admittedly contrived acronym of SALT, we characterize blockchain-based transactions There is a common belief that blockchains have the – from a transactions perspective – as Sequential, potential to fundamentally disrupt entire industries. Agreed, Ledgered, and Tamper-resistant, and – from Whether we are talking about financial services, the a systems perspective – as Symmetric, Admin-free, sharing economy, the Internet of Things, or future en- Ledgered, and Time-consensual.
    [Show full text]
  • Failures in DBMS
    Chapter 11 Database Recovery 1 Failures in DBMS Two common kinds of failures StSystem filfailure (t)(e.g. power outage) ‒ affects all transactions currently in progress but does not physically damage the data (soft crash) Media failures (e.g. Head crash on the disk) ‒ damagg()e to the database (hard crash) ‒ need backup data Recoveryyp scheme responsible for handling failures and restoring database to consistent state 2 Recovery Recovering the database itself Recovery algorithm has two parts ‒ Actions taken during normal operation to ensure system can recover from failure (e.g., backup, log file) ‒ Actions taken after a failure to restore database to consistent state We will discuss (briefly) ‒ Transactions/Transaction recovery ‒ System Recovery 3 Transactions A database is updated by processing transactions that result in changes to one or more records. A user’s program may carry out many operations on the data retrieved from the database, but the DBMS is only concerned with data read/written from/to the database. The DBMS’s abstract view of a user program is a sequence of transactions (reads and writes). To understand database recovery, we must first understand the concept of transaction integrity. 4 Transactions A transaction is considered a logical unit of work ‒ START Statement: BEGIN TRANSACTION ‒ END Statement: COMMIT ‒ Execution errors: ROLLBACK Assume we want to transfer $100 from one bank (A) account to another (B): UPDATE Account_A SET Balance= Balance -100; UPDATE Account_B SET Balance= Balance +100; We want these two operations to appear as a single atomic action 5 Transactions We want these two operations to appear as a single atomic action ‒ To avoid inconsistent states of the database in-between the two updates ‒ And obviously we cannot allow the first UPDATE to be executed and the second not or vice versa.
    [Show full text]
  • ACID Compliant Distributed Key-Value Store
    ACID Compliant Distributed Key-Value Store #1 #2 #3 Lakshmi Narasimhan Seshan ,​ Rajesh Jalisatgi ,​ Vijaeendra Simha G A # ​ ​ ​ ​1l​ [email protected] # ​2r​ [email protected] #3v​ [email protected] Abstract thought that would be easier to implement. All Built a fault-tolerant and strongly-consistent key/value storage components run http and grpc endpoints. Http endpoints service using the existing RAFT implementation. Add ACID are for debugging/configuration. Grpc Endpoints are transaction capability to the service using a 2PC variant. Build used for communication between components. on the raftexample[1] (available as part of etcd) to add atomic Replica Manager (RM): RM is the service discovery transactions. This supports sharding of keys and concurrent transactions on sharded KV Store. By Implementing a part of the system. RM is initiated with each of the transactional distributed KV store, we gain working knowledge Replica Servers available in the system. Users have to of different protocols and complexities to make it work together. instantiate the RM with the number of shards that the user wants the key to be split into. Currently we cannot Keywords— ACID, Key-Value, 2PC, sharding, 2PL Transaction dynamically change while RM is running. New Replica ​ ​ Servers cannot be added or removed from once RM is I. INTRODUCTION ​ up and running. However Replica Servers can go down Distributed KV stores have become a norm with the and come back and RM can detect this. Each Shard advent of microservices architecture and the NoSql Leader updates the information to RM, while the DTM revolution. Initially KV Store discarded ACID properties leader updates its information to the RM.
    [Show full text]
  • Lecture 15: March 28 15.1 Overview 15.2 Transactions
    CMPSCI 677 Distributed and Operating Systems Spring 2019 Lecture 15: March 28 Lecturer: Prashant Shenoy 15.1 Overview This section covers the following topics: Distributed Transactions: ACID Properties, Concurrency Control, Serializability, Two-Phase Locking 15.2 Transactions Transactions are used widely in databases as they provide atomicity (all or nothing property). Atomicity is the property in which operations inside a transaction all execute successfully or none of the operations execute. Thus, if a process crashes during a transaction, all operations that happened during that transaction must be undone. Transactions are usually implemented using locks. Without locks there would be interleaving of operations from two transactions, causing overwrites and inconsistencies. It has to look like all instructions/operations of one transaction are executed at once, while ensuring other external instructions/operations are not executing at the same time. This is especially important in real-world applications such as banking applications. 15.2.1 ACID: Most transaction systems will provide the following properties • Atomicity: All or nothing (all instructions execute or none; cannot have some instructions execute and some do not) • Consistency: Transaction takes system from one consistent (valid) state to another • Isolated: Transaction executes as if it is the only transaction in the system. Ensures that the concurrent execution of transactions results in a system state that would be obtained if transactions were executed sequentially (serializability).
    [Show full text]
  • What Is a Database Management System? What Is a Transaction
    What is a Database? Collection of data central to some enterprise Overview of Databases and Essential to operation of enterprise Transaction Processing Contains the only record of enterprise activity An asset in its own right Chapter 1 Historical data can guide enterprise strategy Of interest to other enterprises State of database mirrors state of enterprise Database is persistent 2 What is a Database Management What is a Transaction? System? When an event in the real world changes the A Database Management System (DBMS) state of the enterprise, a transaction is is a program that manages a database: executed to cause the corresponding change in the database state Supports a high-level access language (e.g. With an on-line database, the event causes the SQL). transaction to be executed in real time Application describes database accesses using A transaction is an application program that language. with special properties - discussed later - to DBMS interprets statements of language to guarantee it maintains database correctness perform requested database access. 3 4 What is a Transaction Processing Transaction Processing System System? Transaction execution is controlled by a TP monitor s DBMS database n o i Creates the abstraction of a transaction, t c a analogous to the way an operating system s n a r creates the abstraction of a process t DBMS database TP monitor and DBMS together guarantee the special properties of transactions TP Monitor A Transaction Processing System consists of TP monitor, databases, and transactions 5 6 1 System
    [Show full text]
  • What Is Nosql? the Only Thing That All Nosql Solutions Providers Generally Agree on Is That the Term “Nosql” Isn’T Perfect, but It Is Catchy
    NoSQL GREG SYSADMINBURD Greg Burd is a Developer Choosing between databases used to boil down to examining the differences Advocate for Basho between the available commercial and open source relational databases . The term Technologies, makers of Riak. “database” had become synonymous with SQL, and for a while not much else came Before Basho, Greg spent close to being a viable solution for data storage . But recently there has been a shift nearly ten years as the product manager for in the database landscape . When considering options for data storage, there is a Berkeley DB at Sleepycat Software and then new game in town: NoSQL databases . In this article I’ll introduce this new cat- at Oracle. Previously, Greg worked for NeXT egory of databases, examine where they came from and what they are good for, and Computer, Sun Microsystems, and KnowNow. help you understand whether you, too, should be considering a NoSQL solution in Greg has long been an avid supporter of open place of, or in addition to, your RDBMS database . source software. [email protected] What Is NoSQL? The only thing that all NoSQL solutions providers generally agree on is that the term “NoSQL” isn’t perfect, but it is catchy . Most agree that the “no” stands for “not only”—an admission that the goal is not to reject SQL but, rather, to compensate for the technical limitations shared by the majority of relational database implemen- tations . In fact, NoSQL is more a rejection of a particular software and hardware architecture for databases than of any single technology, language, or product .
    [Show full text]
  • Damage Management in Database Management Systems
    The Pennsylvania State University The Graduate School Department of Information Sciences and Technology Damage Management in Database Management Systems A Dissertation in Information Sciences and Technology by Kun Bai °c 2010 Kun Bai Submitted in Partial Ful¯llment of the Requirements for the Degree of Doctor of Philosophy May 2010 The dissertation of Kun Bai was reviewed and approved1 by the following: Peng Liu Associate Professor of Information Sciences and Technology Dissertation Adviser Chair of Committee Chao-Hsien Chu Professor of Information Sciences and Technology Thomas La Porta Distinguished Professor of Computer Science and Engineering Sencun Zhu Assistant Professor of Computer Science and Engineering Frederico Fonseca Associate Professor of Information Sciences and Technology Associate Dean, College of Information Sciences and Technology 1Signatures on ¯le in the Graduate School. iii Abstract In the past two decades there have been many advances in the ¯eld of computer security. However, since vulnerabilities cannot be completely removed from a system, successful attacks often occur and cause damage to the system. Despite numerous tech- nological advances in both security software and hardware, there are many challenging problems that still limit e®ectiveness and practicality of existing security measures. As Web applications gain popularity in today's world, surviving Database Man- agement System (DBMS) from an attack is becoming even more crucial than before because of the increasingly critical role that DBMS is playing in business/life/mission- critical applications. Although signi¯cant progress has been achieved to protect the DBMS, such as the existing database security techniques (e.g., access control, integrity constraint and failure recovery, etc.,), the buniness/life/mission-critical applications still can be hit due to some new threats towards the back-end DBMS.
    [Show full text]
  • ACID, Transactions
    ECE 650 Systems Programming & Engineering Spring 2018 Database Transaction Processing Tyler Bletsch Duke University Slides are adapted from Brian Rogers (Duke) Transaction Processing Systems • Systems with large DB’s; many concurrent users – As a result, many concurrent database transactions – E.g. Reservation systems, banking, credit card processing, stock markets, supermarket checkout • Need high availability and fast response time • Concepts – Concurrency control and recovery – Transactions and transaction processing – ACID properties (desirable for transactions) – Schedules of transactions and recoverability – Serializability – Transactions in SQL 2 Single-User vs. Multi-User • DBMS can be single-user or multi-user – How many users can use the system concurrently? – Most DBMSs are multi-user (e.g. airline reservation system) • Recall our concurrency lectures (similar issues here) – Multiprogramming – Interleaved execution of multiple processes – Parallel processing (if multiple processor cores or HW threads) A A B B C CPU1 D CPU2 t1 t2 t3 t4 time Interleaved concurrency is model we will assume 3 Transactions • Transaction is logical unit of database processing – Contains ≥ 1 access operation – Operations: insertion, deletion, modification, retrieval • E.g. things that happen as part of the queries we’ve learned • Specifying database operations of a transaction: – Can be embedded in an application program – Can be specified interactively via a query language like SQL – May mark transaction boundaries by enclosing operations with: • “begin transaction” and “end transaction” • Read-only transaction: – No database update operations; only retrieval operations 4 Database Model for Transactions • Database represented as collection of named data items – Size of data item is its “granularity” – E.g. May be field of a record (row) in a database – E.g.
    [Show full text]
  • Concurrency Control Basics
    Outline l Introduction/problems, l definitions Introduction/ (transaction, history, conflict, equivalence, Problems serializability, ...), Definitions l locking. Chapter 2: Locking Concurrency Control Basics Klemens Böhm Distributed Data Management: Concurrency Control Basics – 1 Klemens Böhm Distributed Data Management: Concurrency Control Basics – 2 Atomicity, Isolation Synchronisation, Distributed (1) l Transactional guarantees – l Essential feature of databases: in particular, atomicity and isolation. Many users can access the same data concurrently – be it read, be it write. Introduction/ l Atomicity Introduction/ Problems Problems u Example, „bank scenario“: l Consistency must be guaranteed – Definitions Definitions task of synchronization component. Locking Number Person Balance Locking Klemens 5000 l Multi-user mode shall be hidden from users as far as possible: concurrent processing Gunter 200 of requests shall be transparent, u Money transfer – two elementary operations. ‚illusion‘ of being the only user. – debit(Klemens, 500), – credit(Gunter, 500). l Isolation – can be explained with this example, too. l Transactions. Klemens Böhm Distributed Data Management: Concurrency Control Basics – 3 Klemens Böhm Distributed Data Management: Concurrency Control Basics – 4 Synchronisation, Distributed (2) Synchronization in General l Serial execution of application programs Uncontrolled non-serial execution u achieves that illusion leads to other problems, notably inconsistency: l Introduction/ without any synchronization effort, Introduction/
    [Show full text]