浙江大学数据库系统概念PPT第十六章 对应原版教材第五版
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浙江大学数据库系统概念PPT第十六章-精品文档28页
A locking protocol is a set of rules followed by all transactions while requesting and releasing locks. Locking protocols restrict the set of possible schedules.
Database System Concepts 3rd Edition
16.1
©Silberschatz, Korth and Sudarshan, Bo Zhou
Lock-Based Protocols
A lock is a mechanism to control concurrent access to a data item Data items can be locked in two modes :
Basically, how to generate a correct (serializable) schedule?
Database System Concepts 3rd Edition
16.4
©Silberschatz, Korth and Sudarshan, Bo Zhou
Pitfalls of Lock-Based Protocols
T2: lock-S(A); read (A); unlock(A); lock-S(B); read (B); unlock(B); display(A+B)
Locking as above is not sufficient to guarantee serializability — if A and B get updated in-between the read of A and B, the displayed sum would be wrong.
Database System Concepts 3rd Edition
16.1
©Silberschatz, Korth and Sudarshan, Bo Zhou
Lock-Based Protocols
A lock is a mechanism to control concurrent access to a data item Data items can be locked in two modes :
Basically, how to generate a correct (serializable) schedule?
Database System Concepts 3rd Edition
16.4
©Silberschatz, Korth and Sudarshan, Bo Zhou
Pitfalls of Lock-Based Protocols
T2: lock-S(A); read (A); unlock(A); lock-S(B); read (B); unlock(B); display(A+B)
Locking as above is not sufficient to guarantee serializability — if A and B get updated in-between the read of A and B, the displayed sum would be wrong.
数据库系统概念PPT第一章,对应原版教材第五版
Instance – the actual content of the database at a particular point in time
Analogous to the value of a variable
Physical Data Independence – the ability to modify the physical schema
Security problems
Database systems offer solutions to all the above problems
Database System Concepts
1.5
©Silberschatz, Korth and Sudarshan, Bo Zhou
Data Abstraction
1.6
©Silberschatz, Korth and Sudarshan, Bo Zhou
Levels of Abstraction
A major purpose of database system is to provide an abstract of
view of data, and hide the certain detail of data storage.
Integrity constraints (e.g. account balance > 0) become part
of program code
Hard to add new constraints or change existing ones
Database System Concepts
without changing the logical schema
Analogous to the value of a variable
Physical Data Independence – the ability to modify the physical schema
Security problems
Database systems offer solutions to all the above problems
Database System Concepts
1.5
©Silberschatz, Korth and Sudarshan, Bo Zhou
Data Abstraction
1.6
©Silberschatz, Korth and Sudarshan, Bo Zhou
Levels of Abstraction
A major purpose of database system is to provide an abstract of
view of data, and hide the certain detail of data storage.
Integrity constraints (e.g. account balance > 0) become part
of program code
Hard to add new constraints or change existing ones
Database System Concepts
without changing the logical schema
数据库系统概念原书第5版(英文)第二章PPT课件
9/29/2020
Dept. of Comp. Sci. & Tech.,
4
Example of a Relation
9/29/2020
Dept. of Comp. Sci. & Tech.,
5
Basic Structure
Formally, given sets D1, D2, …. Dn a relation r is a subset of D1 x D2 x … x Dn Thus a relation is a set of n-tuples (a1, a2, …, an) where
• Other Topics: XML, Distributed Databases, Advanced topics……
9/29/2020
Dept. of Comp. Sci. & TRelational Model for Databases Relational Algebra Operations
9/29/2020
Dept. of Comp. Sci. & Tech.,
2
Outline of the Course (2)
• Part 4 Data Storage & Querying
– Chapter 11: Storage and – Chapter 12: Indexing and Hashing – Chapter 13: Query Processing – Chapter 14: Query Optimization
1
Outline of the Course (1)
• Chapter 1: Introduction
Part 1 Relational Databases
浙江大学数据库系统概念PPT第十章,对应原版教材第五版
querying XML documents/data
Database System Concepts 10.5 ©Silberschatz, Korth and Sudarshan, Bo Zhou
Comparison with Relational Data
Inefficient: tags, which in effect represent schema information,
Nesting is supported in object-relational databases
But nesting is appropriate when transferring data
External application does not have direct access to data referenced by a foreign key
<bank-1> <customer> <customer_name> Hayes </customer_name> <customer_street> Main </customer_street> <customer_city> Harrison </customer_city> <account> <account_number> A-102 </account_number> <branch_name> Perryridge </branch_name> <balance> 400 </balance> </account> <account> … </account> </customer> . . </bank-1>
数据库系统概论第五版PDF
数据库系统概论第五版PDF简介《数据库系统概论第五版PDF》是一本介绍数据库系统的入门教材，旨在帮助读者理解数据库系统的基本概念、原理和应用。
本书由柯里斯·李(Morris R. Li)和布鲁斯·斯图尔特(Bruce G. Lindsay)合著，是数据库领域的经典教材之一。
内容概述本书共分为八个章节，每章介绍了数据库系统的不同方面。
下面是各章节的简要概述。
第一章：引论该章节介绍了数据库的基本概念和发展历程。
通过对数据库系统的定义和优势的解释，给读者提供了对数据库系统的初步了解。
第二章：关系数据模型该章节介绍了关系数据模型，包括关系模型的构成要素、关系数据库设计和关系代数。
通过对关系数据模型的详细介绍，读者可以理解关系数据库的基本原理和数据组织方式。
第三章：SQL语言该章节介绍了SQL语言，包括SQL的基本语法、数据的查询和修改操作。
通过对SQL语言的学习和实践，读者可以掌握数据库操作的基本技巧。
第四章：数据库设计该章节介绍了数据库设计的基本原理和方法。
包括数据模型的设计、关系模式的规范化和数据库的物理组织方式。
通过对数据库设计的学习，读者可以理解如何设计一个高效稳定的数据库系统。
第五章：数据库编程该章节介绍了数据库编程的基本概念和技术。
包括存储过程、触发器和函数的编写，以及数据库事务的管理。
通过对数据库编程的学习，读者可以掌握如何编写高效的数据库应用程序。
第六章：关系数据库标准化及数据完整性该章节介绍了关系数据库的标准化和数据完整性保证。
包括关系数据模式的规范化、实体完整性和参照完整性的实现。
通过对数据库标准化和数据完整性的学习，读者可以设计出符合标准和完整性要求的数据库系统。
第七章：物理数据库设计和调优该章节介绍了物理数据库设计和调优的基本原理和方法。
包括数据库索引的设计、查询优化和数据存储方式的选择。
通过对物理数据库设计和调优的学习，读者可以设计出高效的数据库系统和查询方案。
数据库系统概念原书第5版(英文)第一章ppt
Database designers: design database ―schema‖ to model aspects of the real world Database application developers: build applications that interface with databases Database administrators (a.k.a. DBA‘s): load, back up, and restore data, fine-tune databases for performance DBMS implementors: develop the DBMS or specialized data management software, implement new techniques for query processing and optimization inside DBMS
August 15, 2013
Dept. of Comp. Sci. & Tech., Tongji Uni.
4
What is a database?
A very large, integrated collection of data
The amount of data is very large The data is structured and interrelated The data is integrated Entities (e.g., students, courses) Relationships (e.g., Li is taking Database and Knowledge) More recently, also includes active components (e.g. “business logic”)
August 15, 2013
Dept. of Comp. Sci. & Tech., Tongji Uni.
4
What is a database?
A very large, integrated collection of data
The amount of data is very large The data is structured and interrelated The data is integrated Entities (e.g., students, courses) Relationships (e.g., Li is taking Database and Knowledge) More recently, also includes active components (e.g. “business logic”)
浙江大学数据库系统概念十七,对应原版教材第五版
System errors: the database system must terminate an active transaction due to an error condition (e.g., deadlock)
System crash: a power failure or other hardware or software failure causes the system to crash.
Consider transaction Ti that transfers $50 from account A to account B; goal is either to perform all database modifications made by Ti or none at all.
When transaction Ti starts, it registers itself by writing a <Ti start>log record
Before Ti executes write(X), a log record <Ti, X, V1, V2> is written, where V1 is the value of X before the write, and V2 is the value to be written to X.
Database System Concepts
17.7
©Silberschatz, Korth and Sudarshan, Bo Zhou
Implementation of Atomicity and Durability (Cont.)
The shadow-database scheme:
System crash: a power failure or other hardware or software failure causes the system to crash.
Consider transaction Ti that transfers $50 from account A to account B; goal is either to perform all database modifications made by Ti or none at all.
When transaction Ti starts, it registers itself by writing a <Ti start>log record
Before Ti executes write(X), a log record <Ti, X, V1, V2> is written, where V1 is the value of X before the write, and V2 is the value to be written to X.
Database System Concepts
17.7
©Silberschatz, Korth and Sudarshan, Bo Zhou
Implementation of Atomicity and Durability (Cont.)
The shadow-database scheme:
数据库系统概念原书第5版(英文)第一章PPT课件
9/29/2020
Dept. of Comp. Sci. & Tech., Tongji Uni.
4
What is a database?
A very large, integrated collection of data
The amount of data is very large The data is structured and interrelated The data is integrated
9/29/2020
Dept. of Comp. Sci. & Tech., Tongji Uni.
2
Outline of the Course (2)
Part 4 Data Storage & Querying
Chapter 11: Storage and Chapter 12: Indexing and Hashing Chapter 13: Query Processing Chapter 14: Query Optimization
recommendations Manufacturing: production, inventory,
orders, supply chain Human resources: employee records,
salaries, tax deductions
9/29/2020
Dept. of Comp. Sci. & Tech., Tongji Uni.
6
Database Management System (DBMS)
A Database Management System (DBMS) is
a software package designed to store and manage databases
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Any number of transactions can hold shared locks on an item, but if any transaction holds an exclusive on the item no other transaction may hold any lock on the item.
If a lock cannot be granted, the requesting transaction is made to wait till all incompatible locks held by other transactions have been released. The lock is then granted.
Database System Concepts 3rd Edition
16.2
©Silberschatz, Korth and Sudarshan, Bo Zhou
Lock-Based Protocols (Cont.)
Lock-compatibility matrix
A transaction may be granted a lock on an item if the requested lock is compatible with locks already held on the item by other transactions
A locking protocol is a set of rules followed by all transactions while requesting and releasing locks. Locking protocols restrict the set of possible schedules.
Basically, how to generate a correct (serializable) schedule?
Database System Concepts 3rd Edition
16.4
©Silberschatz, Korth and Sudarshan, Bo Zhou
Pitfalls of Lock-Based Protocols
Database System Concepts 3rd Edition
16.1
©Silberschatz, Korth and Sudarshan, Bo Zhou
Lock-Based Protocols
A lock is a mechanism to control concurrent access to a data item Data items can be locked in two modes : 1. exclusive (X) mode. Data item can be both read as well as
written. X-lock is requested using lock-X instruction. 2. shared (S) mode. Data item can only be read. S-lock is
requested using lock-S instruction. Lock requests are made to concurrency-control manager. Transaction can proceed only after request is granted.
Database System Concepts 3rd Edition
16.3
©Silberschatz, Korth and Sudarshan, Bo Zhou
Lock-Based Protocols (Cont.)
Example of a transaction performing locking:
T2: lock-S(A); read (A); unlock(A); lock-S(B); read (B); unlock(B); display(A+B)
Locking as above is not sufficient to guarantee serializability — if A and B get updated in-between the read of A and B, the displayed sum would be wrong.
and its locks released.
Database System Concepts 3rd Edition
16.5
©Silberschatz, Korth and Sudarshan, Bo Zhou
Pitfalls of Lock-Based Protocols (Cont.)
The potential for deadlock exists in most locking protocols. Deadlocks are a necessary evil. Starvation is also possible if concurrency control manager is badly designed. For example:
Chapter 16: Concurrency Control
Lock-Based Protocols Multiple Granularity Deadlock Handling Insert and Delete Operations Concurrency in Index Structures
Consider the partial schedule
Neither T3 nor T4 can make progress — executing lock-S(B) causes T4 to wait for T3 to release its lock on B, while executing lock-X(A) causes T3 to wait for T4 to release its lock on A. Such a situation is called aБайду номын сангаасdeadlock. To handle a deadlock one of T3 or T4 must be rolled back
If a lock cannot be granted, the requesting transaction is made to wait till all incompatible locks held by other transactions have been released. The lock is then granted.
Database System Concepts 3rd Edition
16.2
©Silberschatz, Korth and Sudarshan, Bo Zhou
Lock-Based Protocols (Cont.)
Lock-compatibility matrix
A transaction may be granted a lock on an item if the requested lock is compatible with locks already held on the item by other transactions
A locking protocol is a set of rules followed by all transactions while requesting and releasing locks. Locking protocols restrict the set of possible schedules.
Basically, how to generate a correct (serializable) schedule?
Database System Concepts 3rd Edition
16.4
©Silberschatz, Korth and Sudarshan, Bo Zhou
Pitfalls of Lock-Based Protocols
Database System Concepts 3rd Edition
16.1
©Silberschatz, Korth and Sudarshan, Bo Zhou
Lock-Based Protocols
A lock is a mechanism to control concurrent access to a data item Data items can be locked in two modes : 1. exclusive (X) mode. Data item can be both read as well as
written. X-lock is requested using lock-X instruction. 2. shared (S) mode. Data item can only be read. S-lock is
requested using lock-S instruction. Lock requests are made to concurrency-control manager. Transaction can proceed only after request is granted.
Database System Concepts 3rd Edition
16.3
©Silberschatz, Korth and Sudarshan, Bo Zhou
Lock-Based Protocols (Cont.)
Example of a transaction performing locking:
T2: lock-S(A); read (A); unlock(A); lock-S(B); read (B); unlock(B); display(A+B)
Locking as above is not sufficient to guarantee serializability — if A and B get updated in-between the read of A and B, the displayed sum would be wrong.
and its locks released.
Database System Concepts 3rd Edition
16.5
©Silberschatz, Korth and Sudarshan, Bo Zhou
Pitfalls of Lock-Based Protocols (Cont.)
The potential for deadlock exists in most locking protocols. Deadlocks are a necessary evil. Starvation is also possible if concurrency control manager is badly designed. For example:
Chapter 16: Concurrency Control
Lock-Based Protocols Multiple Granularity Deadlock Handling Insert and Delete Operations Concurrency in Index Structures
Consider the partial schedule
Neither T3 nor T4 can make progress — executing lock-S(B) causes T4 to wait for T3 to release its lock on B, while executing lock-X(A) causes T3 to wait for T4 to release its lock on A. Such a situation is called aБайду номын сангаасdeadlock. To handle a deadlock one of T3 or T4 must be rolled back