Architecture of DBMS

8/6/2019 Architecture of DBMS

1/12

Architecture and Implementation

of Database Management Systems

Prof. Dr. Marc H. Scholl

Summer 2004

University of Konstanz, Dept. of Computer & Information Science

www.inf.uni-konstanz.de/dbis/teaching/ss04/architektur-von-dbms


2/12

Module 1: Introduction & Overview

Module Outline1.1 What its all about

1.2 Outline of the Course

1.3 Organizational Matters

Files and Index Structures

Buffer Manager

Disk Space Manager

RecoveryManager

Plan Executor

Operator Evaluator Optimizer

Parser

ApplicationsWeb Forms SQL Interface

SQL Commands

Query Processor

Concurrency ControlDBMS

Database

Index Files

Data FilesSystem Catalog

TransactionManager

LockManager

2


3/12

1.1 What its all about

While introductory courses have presented the functionality, i.e., the interface, of

database management systems (DBMSs), this course will dive into the internals.

We will, for example, learn how a DBMS can

efficiently organize and access data on disk, knowing that I/O is way more

expensive than CPU cycles,

translate SQL queries into efficient execution plans, including query rewrite

optimization and index exploitation,

sort/combine/filter large data volumes exceeding main memory size by far,

allow many users to consistently access and modify the database at the

same time,

takes care of failures and guarantees recovery into a consistent operation

after crashes.

This is a systems-oriented course, with focus on the necessary infrastructure to

build a DBMS. This will help to thoroughly analyze, compare, and tune DBMSs for

performance-critical applications.3


4/12

1.1.1 Overall System Architecture

A DBMS is typically run as a back-end server in a (local or global) network,

offering services to clients directly or to application servers.

StoredData(Pages)

DataServer

ApplicationServer

ClientsUsers . . .

Application

Program 1

Application

Program 2 ...

...Objects

encapsulateddata

exposeddata

Request Reply

Request Reply

StoredData(Pages)

DataServer

ApplicationServer

ClientsUsers . . .

Application

Program 1

Application

Program 2 ...

...Objects

encapsulateddata

exposeddata

Request Reply

Request Reply

Generally, we call this the 3-tier reference architecture.4


5/12

1.1.2 Layered DBMS Architecture

Typically, a DBMS implements its functionality in a layered architecture that builds

up by incrementally adding more abstractions from the low level of block I/O

devices up to the high level of a declarative (SQL) user interface.

Database

Database

Server

Clients. . .

Requests

Language & Interface Layer

Query Decomposition &Optimization Layer

Query Execution Layer

Access Layer

Storage Layer

DataAccesses

RequestExecutionThreads

Database

Database

Server

Clients. . .

Requests

Language & Interface Layer

Query Decomposition &Optimization Layer

Query Execution Layer

Access Layer

Storage Layer

DataAccesses

RequestExecutionThreads

5


6/12

1.1.3 Storage Structures

Whether the DBMS offers relational, object-relational, or other data structures at

the user interface, internally they have to be mapped into fixed-length blocks that

serve as the basic I/O-unit of transfer between main and secondary memory.

Database

ExtentTable

DatabasePage

Page Header

Slot Array

Ben 55 Las Vegas ...

Sue 23 Seattle...

Joe 29 San Antonio...

free space

forwardingRID

---

Extents

Database

ExtentTable

DatabasePage

Page Header

Slot Array

Ben 55 Las Vegas ...

Sue 23 Seattle...

Joe 29 San Antonio...

free space

forwardingRID

---

Extents6


7/12

1.1.4 Access Paths

A DBMS typically provides a number of indexing techniques that allow for fast

content-based searching of records, such as tree-structured or hash-based

methods. Often, the suite of such indexing techniques can be extended to match

the requirements of particular applications.

Adam Bill Dick Eve Hank JaneBob Jill Tom

Bob Eve Tom

Root Node

Leaf Nodes

RIDs

B+-tree

Adam Bill Dick Eve Hank JaneBob Jill Tom

Bob Eve Tom

Root Node

Leaf Nodes

RIDs

B+-tree

7


8/12

1.1.5 Query Execution

Declarative query specifications, e.g. expressed in SQL, need to be optimized and

transformed into efficient query execution plans (QEPs), i.e., sequential or even

parallelized programs that compute the results.

Index Scanon CityIndex

RID Access

Fetch PersonRecord

Filtering

Projection


RID Access

Fetch PersonRecord

Filtering

Projection

Index Scanon AgeIndex


RID ListIntersection

RID Access

Fetch PersonRecord

Projection

Index Scanon AgeIndex


RID ListIntersection

RID Access

Fetch PersonRecord

Projection

8


9/12

1.1.6 Implementing a Lock Manager

Most DBMSs use a locking protocol (e.g., 2PL) for concurrency control.

Efficiently implementing the lock manager and exploiting the synchronization

primitives offered by the underlying operating system is crucial for a high degree of

parallelism.

.

.

.

.

.

.

Hash Tableindexed byResource Id

...

Transaction Id

Update Flag

Transaction Status

Number of Locks

LCB Chain

Transaction Control Blocks (TCBs)

...

...

Resource Id

Hash Chain

FirstInQueue

Resource Control Blocks (RCBs)

...

Transaction Id

Resource Id

Lock Mode

Lock Control Blocks (LCBs)

Lock Status

NextInQueueLCB Chain

.

.

..

.

.

.

.

.

Hash Tableindexed byResource Id

...

Transaction Id

Update Flag

Transaction Status

Number of Locks

LCB Chain

Transaction Control Blocks (TCBs)

...

...

Resource Id

Hash Chain

FirstInQueue

Resource Control Blocks (RCBs)

...

Transaction Id

Resource Id

Lock Mode

Lock Control Blocks (LCBs)

Lock Status

NextInQueueLCB Chain

.

.

.

9


10/12

1.2 Outline of the Course

We will pursue a bottom-up strategy, starting from the block-I/O devices used for

secondary storage management and work our way up to the SQL interface.

Most part of the lecture is based on the

book (Ramakrishnan and Gehrke, 2003).

Additional references to other textbooks

and related literature will be given when

appropriate.

Files and Index Structures

Buffer Manager

Disk Space Manager

RecoveryManager

Plan Executor

Operator Evaluator Optimizer

Parser

ApplicationsWeb Forms SQL Interface

SQL Commands

Query Processor

Concurrency ControlDBMS

Database

Index Files

Data FilesSystem Catalog

TransactionManager

LockManager

10


11/12

1.3 Organizational Matters

Register with the Account Tool.

Actively participate in lectures and assignments.

There will be a written exam at the end of the semester.

Let us know when you have problems or suggestions.

10 copies of the book underlying this course are available in the U KN library.

11


12/12

Bibliography

Elmasri, R. and Navathe, S. (2000). Fundamentals of Database Systems.

Addison-Wesley, Reading, MA., 3 edition. Titel der deutschen Ausgabe von 2002:

Grundlagen von Datenbanken.Harder, T. (1987). Realisierung von operationalen Schnittstellen, chapter 3. in

(Lockemann and Schmidt, 1987). Springer.

Harder, T. (1999). Datenbanksysteme: Konzepte und Techniken der Implementierung.

Springer.

Heuer, A. and Saake, G. (1999). Datenbanken: Implementierungstechniken. IntlThompson Publishing, Bonn.

Lockemann, P. and Dittrich, K. (1987). Architektur von Datenbanksystemen, chapter 2.

in (Lockemann and Schmidt, 1987). Springer.

Lockemann, P. and Schmidt, J., editors (1987). Datenbank-Handbuch. Springer-Verlag.

Mitschang, B. (1995). Anfrageverarbeitung in Datenbanksystemen - Entwurfs- und

Implementierungsaspekte. Vieweg.

Ramakrishnan, R. and Gehrke, J. (2003). Database Management Systems. McGraw-Hill,

New York, 3 edition.

12

Documents

Architecture of DBMS