Inhomogeneous distributed database all sites have identical software and are aware of each other and agree to cooperate in processing user requests. Each site surrenders part of its autonomy in terms of the right to change schema or software. A homogeneous DBMS appears to the user as a single system. The homogeneous system is much easier to design and manage. The following conditions must be satisfied for the homogeneous database:
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The operating system is used, at each location
must be the same or compatible
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The data structures used at each location must
be same or compatible
In a heterogeneous
distributed database, different sites may use different schema and software. The difference in a schema is a major problem for query processing and transaction
processing. Sites may not be aware of each other and may provide only limited
facilities for cooperation in transaction processing. In heterogeneous systems,
different nodes may have different hardware & software and data structures
at various nodes or locations are also incompatible. Different computers and
operating systems, database applications, or data models may be used at each of
the locations. For example, one location may have the latest relational
database management technology, while another location may store data using
conventional files or old versions of the database management system. Similarly, one
location may have the Windows NT operating system, while another may have UNIX.
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