Download Chapter 13

Chapter 13
Data and Database
Administration
SDLC and the database
development process
SDLC
Project ID
Project init
Database Deliverable
Enterprise model
Conceptual Model
Analysis
Logical design
Physical design
Logical model
Implementation
Maintenance
Working system
Data structures and storage plan
Management
Proper
delivery of information
not only depends on the
capabilities of the computer
hardware and software but also
on the organization’s ability to
manage data as an important
resource
How Does IS Manage Data?

Data Administrators: A high-level function that is
responsible for the overall management of data
resources in an organization, including
maintaining corporate-wide definitions and
standards.

Database Administrators: A technical function that
is responsible for physical database design and
for dealing with technical issues such as security
enforcement, database performance, and backup
and recovery.

Data Stewardship: Manages a specific logical data
resource for all business functions. Distribute
data admin. to those most knowledgeable about
specific data
Data Administration
Functions
 Data
policies, procedures, standards
 Planning
 Data
conflict (ownership) resolution
 Internal
marketing of DA concepts
 Managing
the data repository
Database Administration
Functions
 Selection
 Managing
of hardware and software
data security, privacy, and
integrity
 Data
 Fig.
backup and recovery
13-1 is a list of DA and DBA
functions
Threats to Data Security
 Accidental
losses attributable to:
• Human error.
• Software failure.
• Hardware failure.
 Theft
and fraud.
 Improper
data access:
• Loss of privacy (personal data).
• Loss of confidentiality (corporate data).
 Loss
of data integrity.
 Loss
of availability (through, e.g. sabotage).
Possible locations of data
security threats
Database Security Features
 Protection
of the database against
accidental or intentional loss,
destruction or misuse
• Views
• Authorization rules
• User-defined procedures
• Encryption procedures
• Authentication schemes
Database Security Features
 Views
• Restrict user access to data
• Various ways to get around so not
sufficient measure
 Authorization
Rules
• Controls embedded in DBMS that restrict
user access to data and user actions that
can be enacted on data
– Who can update? Insert? Read?
Authorization matrix
Database Security Features

User-Defined Procedures
• Allows system designers to add other security
features
– Passwords
– Valid procedure name

Encryption
• Coding of data so that it cannot be read by
humans
– Financial and military data
– WWW issues
– Government ability to decode all encryption
schemes
Database Security Features
 Authentication
Schemes
• How to positively identify that person trying
to gain access to a computer resource is
“that” person
–Biometric devices--measure
fingerprints, voice prints, retina prints
–Smart card would have biometric data
embedded
Database Failures
 Aborted
Transactions
• A transaction is not completed
 Incorrect
Data
• data entry error, calculation error, coding error
 System
Failure
• Component failure, power failure
 Database
Destruction
• drive failure, disaster recovery
Database Recovery and Basic
Recovery Facilities

Backup facilities
– Periodic backup copies of entire DB

Journalizing facilities
– Maintain an audit trail of transactions and DB
changes

Checkpoint facilities
– DBMS suspends all processing and synchronizes
files and journals

Recovery manager
– Allows the DBMS to restore the DB to correct
condition and restart
Recovery and Restart
Procedures
 Restore/Rerun
• Reprocess the day’s transactions up to the
point of failure against a backup copy of
the database
• Simple
• Time to reprocess may be prohibitive
• Sequencing of transactions may be
different than when originally run
–withdrawal posted prior to deposit
Recovery and Restart
Procedures
 Transaction
Integrity
• Transaction changes are not made to the
DB until the entire transaction has been
completed and the changes are committed
• If transaction fails at any point, the
transaction is aborted
Recovery and Restart
Procedures
 Backward
Recovery (Rollback)
• Back out of unwanted changes to the database
• Used to reverse the changes that have been
made to transactions that have been aborted
 Forward
Recovery (Rollforward)
• Use an earlier copy of the DB and apply after
images of good transactions
• More accurate and faster than restore/rerun
Basic recovery techniques
(a) Rollback
(b) Rollforward
Concurrency Control
 Concerns
with preventing loss of data
integrity due to interference between users in
a multi-user environment
• Pessimistic approach: interference will always
occur so we LOCK records
• Optimistic approach: interference will rarely occur
so we VERSION records
 Multiple
concurrent updates to a database
can lead to lost updates and therefore to
errors
Lost Update Example
Time
John
Read account Balance
(balance = $1,000)
.
.
.
Withdraw $200
(balance = $800
.
.
.
Write account balance
(balance = $800)
Marsha
Read account balance
(balance = $1,000)
.
.
.
Withdraw $300
(balance = $700)
.
.
.
Write account balance
(balance = $700)
ERROR
Locking

Deny access of data to other users while an
update is underway

Locking level (granularity)
Database - during backups
Table - during batch updates
Block or page - generally not used
Record - Often used
Field - Useful when only one field is likely to
change
Types of Locks
 Shared
• Allows others to read, but not write
• Prevents others from putting Exclusive
lock on the record
 Exclusive
• Denies other access to the record (even
read)
• Necessary when updating the record
Deadlock
(aka: Deadly Embrace)
 Two
or more transactions have placed locks
on record(s) that the others need.
 Each
waits for the other(s) to release
 Requires
DBMS intervention
• Prevention, often not practical
• Resolution, common solution
–Detects deadlock and backs one or
more transactions out, lets one finish,
then restarts next transaction.
Versioning
 Each
transaction is restricted to a view of
the database as of the transaction start
time.
 When
transaction modifies a record, the
DBMS creates a new version of record
instead of overwriting old record
 Changes
to 2 identical views
simultaneously
• First change (according to time stamp) is
enacted
• Second change is informed of conflict and
transaction must be performed again
Versioning
John
Read account Balance
(balance = $1,000)
.
.
.
Withdraw $200
(balance = $800
.
.
.
Commit
Marsha
Read account balance
(balance = $1,000)
.
.
.
Attempt to withdraw $300
(Denied - balance update
conflict)
.
.
Rollback
Restart transaction
Managing Data Quality
 Security
policy and disaster recovery
 Personnel
 Physical
controls
access controls
 Maintenance
controls (hardware &
software)
 Data
protection and privacy
The case...
 What
value did ISBH obtain from the data
architecture project?
 What
should the next step be in order for
ISBH to get the most out of the project?
 What
would you have done differently in
conducting this project?
 What
was Darrell Fisher’s role? Dan
Gurney’s? Were these appropriate?
 What
suggestions would you make to ensure
that ISBH does a better job with Data
Management in the future?