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Data independence can be defined
as the capacity to change the schema at one level without changing the schema
at next higher level. There are two types of data Independence. They are
1. Logical data independence.
2. Physical data independence.
1. Logical data independence is
the capacity to change the conceptual schema without having to change the
external schema.
2. Physical data independence is
the capacity to change the internal schema without changing the conceptual
schema.
When not to use
a DBMS
• Main inhibitors (costs) of
using a DBMS:
• High initial investment and
possible need for additional hardware.
• Overhead for providing
generality, security, concurrency control, recovery, and integrity functions
When a DBMS may be unnecessary:
• If the database and
applications are simple, well defined and not expected to change.
• If there are stringent
real-time requirements that may not be met because of DBMS overhead.
• If access to data by multiple
users is not required.
• When no DBMS may suffice:
• If the database system is not
able to handle the complexity of data because of modeling limitations
• If the database users need special operations not
supported by the DBMS.
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