Images from HELL, by a young Korean Girl
a young Korean artist was shown Hell by Jesus Christ, and told to draw the images that she saw.
Friday, December 21, 2012
Friday, November 16, 2012
DISTRIBUTED DATABASES VS CONVENTIONAL DATABASES
Ø mimics organisational structure with data
Ø local access and autonomy without exclusion
Ø cheaper to create and easier to expand
Ø improved availability/reliability/performance by removing reliance on a
central site
Ø Reduced communication overhead
§
Most data access is local,
less expensive and performs better
Ø Improved processing power
§
Many machines handling the
database rather than a single server
Ø more complex to implement
Ø more costly to maintain
Ø security and integrity control
Ø standards and experience are lacking
Ø Design issues are more complex
1.2 DISTRIBUTED
DATABASES ARCHITECTURE
Ø Defines the structure of the system
o
components
identified
o
functions
of each component defined
o
interrelationships
and interactions between components defined
What is a distributed database?
l“A logically interrelated
collection of shared data (and a description of this data), physically distributed over a computer
network”
Implicit Assumptions
Ø Data stored at a
number of sites ï each site logically
consists of a single processor.
Ø Processors at
different sites are interconnected by a computer network ï no multiprocessors
o parallel database
systems
Ø Distributed
database is a database, not a collection of files ï data logically
related as exhibited in the users’ access patterns
o relational data
model
Ø D-DBMS is a
full-fledged DBMS
o not remote file
system, not a TP system
Advantages of distributed databases
Ø Capacity and incremental growth
Ø Increase reliability and availability
Ø Modularity
Ø Reduced communication overhead
Ø Protection of valuable data
Ø Efficiency and Flexibility
Disadvantages
of distributed databases
Ø DDB design more complex, fragmentation & replication; extra work
must be done by the DBAs to ensure that the distributed nature of the
system is transparent.
Ø Economics,
Ø Concurrency control,
Ø Inexperience,
Ø Security,
Ø Difficult to maintain integrity
Applications
Ø
Manufacturing
- especially multi-plant manufacturing
Ø
Military
command and control
Ø
Electronic
fund transfers and electronic trading
Ø
Corporate
MIS
Ø
Airline
restrictions
Ø
Hotel
chains
Ø
Any
organization which has a decentralized organization structure
Wednesday, November 7, 2012
LECTURE NOTES & ENGINEERING STUDENTS NOTES
LECTURE NOTES & ENGINEERING STUDENTS NOTES FOR DATA STRUCTURES
LECTURE NOTES DBMS
OPERATING
SYSTEM ENGINEERING NOTES
UNIX
NOTES
CORE
JAVA
QUESTION ANSWERS
JAVA
BASICS
ADVANCED
JAVA
PART
OPEN SOURCE LAB(LINUX INSTALLATION ,Kernel Configuration and Installation,.....)
OPEN SOURCE LAB(LINUX INSTALLATION ,Kernel Configuration
and Installation,.....)
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