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The DBMS is a complex software
system.
Typical DBMS Component Modules
The figure is divided into two
halves. The top half of the figure refers to the various users of the database
environment and their interfaces. The lower half shows the internals of the
DBMS responsible for storage of data and processing of transaction.
The database and the DBMS catalog
are usually stored on disk.Access to the disk is primarily controlled by
operating system(OS).which inclues disk input/Output.A higher level stored data
manager module of DBMS controls access to DBMS information that is stored on
the disk.
If we consider the top half of
the figure, It shows interfaces to DBA staff, casual users, application
programmers and parametric users
The DDL compiler processes schema
definitions, specified in the DDL,and stores the description of the schema in
the DBMS Catalog..The catalog includes information such as names and sizes of
the sizes of the files, data types of data of data items. Storage details of
each file, mapping information among schemas and constraints.
Casual users and persons with
occasional need of information from database interact using some for of
interface which is interactive query interface. The queries are parsed, analysed
for correctness of the operations for
the model. the names of the data
elements and so on by a query compiler that compiles them into internal form.
The internal query is subjected to query optimization..The query optimizer is
concerned with rearrangement and possible recording of operations, eliminations
of redundancies.
Application programmer writes
programs in host languages. The precompiler extracts DML commands from an
application program
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