Database Reference
In-Depth Information
Concurrency control.
Guarantees database consistency when transactions execute
simultaneously.
Reliability and recovery.
Provides the ability to recover from failures.
Security.
Has facilities to protect the database from unauthorized access.
Scalability.
Has capabilities to perform adequately even when data and transaction
volumes increase.
Data distribution.
Enables data to be partitioned and distributed among various
physical locations.
Let us leave the topic of OODBMSs by listing their advantages and
disadvantages.
Advantages
•
Enhanced modeling of real-world information based on object orientation
•
Ability to build new abstract data types
•
Benefits of generalization and specialization resulting from provisions for
defining superclasses and subclasses
•
More feasible schema evolution because of the tight coupling between data and
applications
•
Ability to process transactions running for long durations without
difficulty
•
Capability to support sophisticated applications such as CAD and multimedia
systems
Disadvantages
•
O-O data model lacks solid theoretical foundation
•
Complexity of OODBMS—data model slanted toward the programmer, not
the end user
•
Lacks the level of usage and experience of other data models
•
Standards not firmed up
•
Performance compromised by object-level locking for concurrency control
•
No support for user views of data as in relational systems
•
Security mechanisms not quite adequate
OBJECT-RELATIONAL DATABASES
As you know, relational DBMSs are more widely used than any other types of
database systems. Object-oriented database systems started out to support special
applications in engineering, telecommunications, and finance. Even though object-
oriented databases are preferred for such applications, the extent of usage of these
databases is still small compared to that of relational databases.
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