Database distribution Database design
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One DBH - multiple databases
This constellation is also referred to as multi-DB operation . Many application programs work
with two or more databases simultaneously. An application program (AP) may access
several databases within a single transaction. The DBH controls the processing of the
databases and ensures the consistency of all the data re sources.
The databases that are operated by a DBH are part of a data base configuration.
Figure 6: Multi-DB operation
Reasons for distributing data over multiple databases:
– Data that is used only at certain times o r for certain tasks can be stored in a separate
database, which need not be connected the whole time.
– A large-scale database project is more easily implemente d by gradually developing
additional databases.
AP1 AP2 AP3
DB1 DB2 DB3
DBH
DB1 DB2 DB3 DB1 DB3DB1
AP1 AP2 AP3 AP1 AP1 AP3
Configuration