Active databases automatically respond to events inside or outside the system using rules. Main memory databases reside permanently in main memory for faster access than disk-based databases. Active databases support event detection and rule-based responses, while main memory databases have direct memory access without disk overhead. Both have applications in real-time systems where speed is critical.

1. ACTIVE AND MAIN
MEMORY DATABASE
By
Preetam Rajkhowa
Roll no 21
MCA 4th Semester
CCS, DU

2. CONTENTS
• INTRODUCTION
• DEFINITION
• ADVANTAGES AND DISADVANTAGES
• APPLICATIONS
• CURRENT RESEARCH
• FUTURE WORK
• CONCLUSION
• REFERRENCE

3. INTRODUCTION
ACTIVE DATABASE:
Active database are database systems that supports mechanisms that
enable them to respond automatically to events that are taking place
either inside or outside the database system itself by supporting the
specification and implementation of reactive behaviour. The reactive
behaviour resides on rules which integrate cause with an expected
effect.
MAIN MEMORY DATABASE:
Main Memory Database resides permanently in the Main Memory of
the system. There is a backup copy of the database that is stored on
the disk. It primarily relies on main memory for computer data storage
and is contrasted with database management systems that employ a
disk storage mechanism. It is also known as In Memory Database.

4. DEFINITION OF ACTIVE
DATABASE
It is a type of database system that uses Event Driven
Architecture often in the form of ECA rules which responds to
conditions both inside and outside the database. They are
invoked by synchronous events generated by user or application
programs as well as external asynchronous data change events
such as a change in sensor value or time.

5. ACTIVE RULES/PRODUCTION
RULES
They are stored programs which are automatically triggered
when an event occurs. Triggers can be written in response to
Data Manipulation Language (DML) or Data Definition Language
(DDL) or the Database Operations.
The desired reactive behaviour is expressed in terms of
Production Rules which are designed and stored in the Database.
The benefit is that the rules can be shared by many application
programs and the database can optimise their implementation.

6. FEATURES OF ACTIVE DATABASE
• It possess all the concepts of a conventional database i.e. data
modelling facilities, query language etc.
• It supports all the functions of a traditional database like data
definition, data manipulation, storage management etc.
• It supports definition and management of ECA rules.
• It detects event occurrence.
• It must be able to evaluate conditions and to execute actions.
It means that it has to implement rule execution.

7. DEFINITION OF MAIN MEMORY
DATABASE
Main Memory database is the database system that primarily
relies on main memory for computer data storage. They are
faster than disk-optimized databases because disk access is
slower than memory access, the internal optimization are simpler
and execute fewer CPU instructions.

8. FEATURES OF MAIN MEMORY
DATABASE
• Data can be directly accessed and uses shared memory
architecture.
• There are no network overhead or data copies.
• They are tightly coupled.
• They are highly concurrent.
• Fully ACID transactions.

9. ADVANTAGES OF ACTIVE
DATABASE
• Active database systems enhance traditional database
functionalities with powerful rule processing capabilities.
• Triggers in active database enable a uniform and centralized
description of the business rules relevant to system.
• It facilities the maintenance of the business rules.
• The layered approach is beneficial for active object oriented
databases if the base system is in turn implemented in an
object oriented way such that functionality to be written can
be easily modified or wrapped.

10. DISADVANTAGE OF ACTIVE
DATABASE
• Insufficient methodological support in design and analysis.
• Lack of standardization.
• Missing development and administration tools for triggers.
• Weak performance.
• Lack of support for application development.

11. ADVANTAGE OF MAIN MEMORY
DATABASE
• It has direct access to data and uses shared memory
architecture.
• It is handwritten using atomic instructions.
• It has fixed and variable size allocators.
• Code segments which are performance critical are tightly
coupled.

12. DISADVANTAGES OF MAIN
MEMORY DATABASE
• They may not be cost effective.
• There may be risk of data loss.
• There is a limit in the database.

13. APPLICATIONS OF ACTIVE
DATABASE
• Data monitoring activities such as Telecommunications
Network Management, Program trading, Medical and
Financial Decision Support etc.
• Production control activities such as power plants.
• Maintenance task activities e.g. inventory control systems.
• Air traffic control, Computer interrogated manufacturing,
Statistic gathering and authorization tools etc.

14. APPLICATIONS OF MAIN MEMORY
DATABASE
• Used in real time embedded systems.
• Manage the music databases in a MP3 player.
• Programming data in set-top boxes, arithmetic trading and
other financial applications.
• E- Commerce and Social Networking sites.

15. CURRENT RESEARCH OF ACTIVE
DATABASES
• A new condition called Petri Nets is proposed to approach the
model and rules of ECA. It can integrate the rules and is also
independent of the original database.
• A study for concurrency control is going on for real time
active database systems where they are exploring the
dynamics of transaction processing for real time active
databases.
• A research for real time event control in active databases is
being carried out.

16. CURRENT RESEARCH OF MAIN
MEMORY DATABASES
• A research for the implementation techniques for Main
Memory Databases is being carried out where evaluation of
AVL vs B+ tree access methods for the said database is done.

17. FUTURE WORK ON ACTIVE
DATABASE
• Research for new ECA rules.
• Controlling data concurrency in real time.

18. FUTURE WORK ON MAIN
MEMORY DATABASE
• Research for Disaster Recovery of the database.
• Extension of the model for unstructured data structures.
• Life cycle based data management is based on the semantics
of different applications it is possible to specify if a single
record is ever modifies again or remains read-only and thus
allows different strategies for compression and partitioning.

19. CONCLUSION
• Active databases are those types of databases that have the
mechanism to automatically respond to events in the system
where as Main memory databases are the databases that
reside permanently in main memory.
• Active database includes an event driven architecture. Main
memory database completely relies on main memory for
computer data storage.
• Most modern relational databases include active database in
the form of database triggers. Main memory databases are
quite faster.

20. REFERRENCE
• https://en.wikipedia.org/wiki/Active_database
• https://en.wikipedia.org/wiki/In-memory_database
• www.slideshare.net
• Database System Concepts by Silberschatz−Korth−Sudarshan

21. THANK YOU