PENGANTAR MANAJEMEN BASIS DATA

PENGANTAR MANAJEMEN
BASIS DATA
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Pengenalan Database
Konsep dasar database, DBMS
•  Basis data menyediakan fasilitas atau
mempermudah dalam menghasilkan
informasi yang digunakan oleh pemakai
untuk mendukung pengambilan keputusan
•  contoh penggunaan Aplikasi basis data
dalam dunia bisnis : ……?
Sistem Pemrosesan Berkas
Tradisional
•  Bentuk
pemrosesan dasar
yang lahir sebelum
database muncul
•  Berkecunderungan
tidak berbagi
berkas (Setiap
aplikasi memiliki
berkas tersendiri)
Aplikasi
Personalia
Personalia
Aplikasi
Pelatihan
Pelatihan
Kelemahannya dari sistem
pemrosesan berkas tradisional
1. Timbulnya data rangkap (redundancy data) dan
Ketidakkonsistensi data (Inconsistency data)
2. Kesukaran dalam Mengakses Data
3. Data terisolir (Isolation Data)
4. Masalah Pengamanan ( Security Problem )
5. Data Dependence
Sistem Basis data
•  Seiring dengan berjalannya waktu, lambat
laun sistem pemrosesan file mulai
ditinggalkan karena masih bersifat
manual, yang kemudian dikembangkanlah
sistem pemrosesan dengan pendekatan
basis data.
GAMBAR MENJADI SPT APA?
Definisi Database
•  “a collection of related data” (Elmazri &
Navathe, 1994)
•  “an organized collection of logically related
data” (McFadden, Hoffer, and Presscot,
2002)
•  “a collection of data, typically describing
the activities of one or more related
organizations” (Ramakrishnan & Gerke,
2000)
Data dan Basis Data
•  Data adalah representasi fakta dunia nyata
yang mewakili suatu objek seperti manusia
(pegawai, mahasiswa, pembeli), barang,
hewan, peristiwa, konsep, keadaan, dan
sebagainya yang direkam dalam bentu
angka, huruf, simbol, teks, gambar, bunyi
atau kombinasinya.
•  Basis Data adalah sekumpulan data yang
terintegrasi yang diorganisasikan untuk
memenuhi kebutuhan para pemakai di dalam
suatu organisasi.
•  DBMS (Database Management System)
adalah Perangkat Lunak yang menangani
semua pengaksesan ke basis data
•  Sistem Basis Data terdiri dari basis data
dan DBMS
Istilah - Istilah Dasar Basis Data
•  Enterprise
• Bentuk organisasi :………?
• Data operasional : ……….?
•  Entitas
•  Contoh Entitas
•  Atribut (Elemen Data)
•  Nilai Data (Data Value)
•  Kunci Elemen Data (Key Data Element)
•  Record Data
Pengguna Basis Data
•  1. System Engineer
•  2. Database Administrator (DBA)
•  3. End User (Pemakai Akhir)
–  a. Programmer aplikasi
–  b. Pemakai Mahir (Casual User)
–  c. Pemakai Umum (End User / Naïve User)
–  d. Pemakai Khusus (Specialized/
Sophisticated User)
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DBA SKILLS
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Levels of Abstraction
•  Many views, single
conceptual (logical)
schema and physical
schema.
– 
– 
– 
Views describe how users
see the data.
Conceptual schema defines
logical structure
Physical schema describes
the files and indexes used.
View 1
View 2
View 3
Conceptual Schema
Physical Schema
☛  Schemas are defined using DDL; data is modified/queried using DML.
Example: University Database
•  Conceptual schema:
–  Students(sid: string, name: string, login: string,
age: integer, gpa:real)
–  Courses(cid: string, cname:string, credits:integer)
–  Enrolled(sid:string, cid:string, grade:string)
•  Physical schema:
–  Relations stored as unordered files.
–  Index on first column of Students.
•  External Schema (View):
–  Course_info(cid:string,enrollment:integer)
Application Programs
Queries
Database
Schema
DML Preprocessor
Query Processor
DDL
Compiler
Programs Object Code
Database Manager
Dictionary
Manager
Access
Method
File
Manager
DBMS (Database Management System)
System
Buffer
Database dan Data Dic4onary
Komponen DBMS
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Contoh-contoh Basis Data
Relasional :
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DB2 à IBM
ORACLE à Oracle
SYBASE à Powersoft
INFORMIX à Informix
Microsoft Access à Microsoft
MySQL
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Concurrency Control
•  Concurrent execution of user programs is essential
for good DBMS performance.
–  Because disk accesses are frequent, and
relatively slow, it is important to keep the cpu
humming by working on several user programs
concurrently.
•  Interleaving actions of different user programs can
lead to inconsistency: e.g., check is cleared while
account balance is being computed.
•  DBMS ensures such problems don’t arise: users
can pretend they are using a single-user system.
Concurrency Control
•  Concurrency control ensures that one
user’s work does not inappropriately
influence another user’s work
–  No single concurrency control technique is
ideal for all circumstances
–  Trade-offs need to be made between level of
protection and throughput
Atomic Transactions
•  A transaction, or logical unit of work (LUW), is a
series of actions taken against the database that
occurs as an atomic unit
–  Either all actions in a transaction occur or
none of them do
Example: Atomic Transaction
Example: Atomic Transaction
Concurrent Transaction
•  Concurrent transactions refer to two or more
transactions that appear to users as they are being
processed against a database at the same time
•  In reality, CPU can execute only one instruction at a
time
–  Transactions are interleaved meaning that the
operating system quickly switches CPU services
among tasks so that some portion of each of
them is carried out in a given interval
•  Concurrency problems: lost update and inconsistent
reads
Example: Concurrent
Transactions
Example: Lost Update
Problem
Resource Locking
•  Resource locking prevents multiple applications
from obtaining copies of the same record when
the record is about to be changed
Lock Terminology
•  Implicit locks are locks placed by the DBMS
•  Explicit locks are issued by the application program
•  Lock granularity refers to size of a locked resource
–  Rows, page, table, and database level
–  Large granularity is easy to manage but frequently
causes conflicts
•  Types of lock
–  An exclusive lock prohibits other users from reading
the locked resource
–  A shared lock allows other users to read the locked
resource, but they cannot update it
Example: Explicit Locks
Deadlock
•  Deadlock, or the deadly embrace, occurs
when two transactions are each waiting on
a resource that the other transaction holds
Example: Deadlock
Deadlock
•  Preventing deadlock
–  Allow users to issue all lock requests at one time
–  Require all application programs to lock
resources in the same order
•  Breaking deadlock
–  Almost every DBMS has algorithms for detecting
deadlock
–  When deadlock occurs, DBMS aborts one of the
transactions and rollbacks partially completed
work
Declaring Lock Characteristics
•  Most application programs do not explicitly declare
locks due to its complication
•  Instead, they mark transaction boundaries and
declare locking behavior they want the DBMS to use
–  Transaction boundary markers: BEGIN, COMMIT,
and ROLLBACK TRANSACTION
•  Advantage
–  If the locking behavior needs to be changed, only
the lock declaration need be changed, not the
application program
Example: Marking Transaction
Boundaries
Database Security
•  Database security ensures that only
authorized users can perform authorized
activities at authorized times
•  Developing database security
–  Determine users’ processing rights and
responsibilities
–  Enforce security requirements using security
features from both DBMS and application
programs
DBMS Security
•  DBMS products provide security facilities
•  They limit certain actions on certain objects to
certain users or groups
•  Almost all DBMS products use some form of
user name and password security
DBMS Security Model
DBMS Security Guidelines
•  Run DBMS behind a firewall, but plan as though the firewall has been
breached
•  Apply the latest operating system and DBMS service packs and fixes
•  Use the least functionality possible
– 
– 
– 
– 
Support the fewest network protocols possible
Delete unnecessary or unused system stored procedures
Disable default logins and guest users, if possible
Unless required, never allow all users to log on to the DBMS interactively
•  Protect the computer that runs the DBMS
–  No user allowed to work at the computer that runs the DBMS
–  DBMS computer physically secured behind locked doors
–  Access to the room containing the DBMS computer should be recorded in
a log
• 
DBMS Security Guidelines
(cont.)
Manage accounts and passwords
– 
– 
– 
– 
– 
– 
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Use a low privilege user account for the DBMS service
Protect database accounts with strong passwords
Monitor failed login attempts
Frequently check group and role memberships
Audit accounts with null passwords
Assign accounts the lowest privileges possible
Limit DBA account privileges
•  Planning
–  Develop a security plan for preventing and detecting security
problems
–  Create procedures for security emergencies and practice them
Application Security
•  If DBMS security features are inadequate, additional security
code could be written in application program
–  Application security in Internet applications is often provided on the
Web server computer
•  However, you should use the DBMS security features first
–  The closer the security enforcement is to the data, the less chance
there is for infiltration
–  DBMS security features are faster, cheaper, and probably result in
higher quality results than developing your own
Database Recovery
•  In the event of system failure, that
database must be restored to a usable
state as soon as possible
•  Two recovery techniques:
–  Recovery via reprocessing
–  Recovery via rollback/rollforward
Recovery via Reprocessing
•  Recovery via reprocessing: the database
goes back to a known point (database
save) and reprocesses the workload from
there (re-execute all database update
programs)
•  Unfeasible strategy because
–  The recovered system may never catch up if
the computer is heavily scheduled
–  Asynchronous events, although concurrent
transactions, may cause different results
Rollback/Rollforward
•  Recovery via rollback/rollforward:
–  Periodically save the database and keep a
database change log since the save
•  Database log contains records of the data
changes in chronological order
•  When there is a failure, either rollback or rollforward
is applied
–  Rollback: undo the erroneous changes made to
the database and reprocess valid transactions
–  Rollforward: restored database using saved data
and valid transactions since the last save
Example: Rollback
•  Before-images: a copy of every
database record (or page) before it was
changed
Example: Rollforward
•  After-images: a copy of every database
record (or page) after it was changed
Example: Transaction Log
Checkpoint
•  A checkpoint is a point of synchronization between the
database and the transaction log
–  DBMS refuses new requests, finishes processing
outstanding requests, and writes its buffers to disk
–  The DBMS waits until the writing is successfully
completed à the log and the database are
synchronized
•  Checkpoints speed up database recovery process
–  Database can be recovered using after-images
since the last checkpoint
–  Checkpoint can be done several times per hour
•  Most DBMS products automatically checkpoint
themselves
Overview of System Architecture
Database Server
Database Cache
read
write
begin
Database
Page
commit, rollback
write
Volatile
Memory
Stable
Storage
Stable
Database
fetch
Database
Page
flush
Log Buffer
Log Entry
force
Stable
Log
Log Entry
Databases make these folks
happy ...
•  End users and DBMS vendors
•  DB application programmers
– 
E.g. smart webmasters
•  Database administrator (DBA)
Designs logical /physical schemas
–  Handles security and authorization
–  Data availability, crash recovery
–  Database tuning as needs evolve
– 
Must understand how a DBMS works!
Structure of a DBMS
•  A typical DBMS has a
layered architecture.
•  The figure does not
show the concurrency
control and recovery
components.
•  This is one of several
possible architectures;
each system has its
own variations.
These layers
must consider
concurrency
control and
recovery
Query Optimization
and Execution
Relational Operators
Files and Access Methods
Buffer Management
Disk Space Management
DB
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TUGAS
1.  Tugas per kelompok, 1 kelompok : …mhs
2.  Per kelompok tentukan contoh kasus
suatu sistem informasi atau aplikasi
bebas yang digunakan pada satu
organisasi. Misal : Aplikasi ATM
Contoh kasus tidak harus seluruh sistem
atau aplikasi, satu subsistem atau satu
modul saja.
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3. Dari contoh kasus yang sudah ditentukan
buat Rancangan Database dan
Implementasi nya secara sederhana.
Rancangan database dapat menggunakan
alat bantu ERD atau Class Diagram
4. Aplikasi sederhana, buat tampilan input
dan output yang merepresentasi rancangan
database yang telah dibuat.
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Contoh :
•  Aplikasi ATM untuk Modul Informasi Saldo
•  Rancangan Database
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•  Form Input
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•  OUTPUT
Nomor Rekening : ….
Nama
: ….
Saldo
: X.XXX.XXX
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FORMAT PRESENTASI
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NAMA SISTEM INFORMASI
GAMBARAN UMUM SISTEM INFORMASI
SUB SISTEM
RANCANGAN DATABASE
APLIKASI SEDERHANA à LANGSUNG
KE PROGRAM
–  INPUT
–  OUTPUT
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