Page 14 - DCAP402_DCAO204_DATABASE MANAGEMENT SYSTEM_MANAGING DATABASE

Unit 1: Database Fundamentals

2. Embedded DML Pre-compiler: It converts DML statements embedded in an application Notes
program to normal procedure calls in the host language. The pre-compiler must interact
with the DML compiler to generate the appropriate code.
3. DDL Interpreter: It interprets DDL Stateline its and records them in a set of tables containing
metadata.

4. Transaction Manager: Ensures that the database remains in a consistent (correct) state
despite system failures, and that concurrent transaction executions proceed without
conflicting.
5. File Manager: Manages the allocation of space on disk storage and the data structures used
to represent information stored on disk.

6. Buffer Manager: Is responsible for fetching data from disk storage into main memory and
deciding what data to cache in memory.
Also some data structures are required as part of the physical system implementation:

1. Data Files: The data files store the database by itself.
2. Data Dictionary: It stores metadata about the structure of the database, as it is used
heavily.

3. Indices: It provides fast access to data items that hold particular values.
4. Statistical Data: It stores statistical information about the data in the database. This
information used by the query processor to select efficient ways to execute a query.

Figure 1.3: Structure of DBMS

Application programmes
APPLICATION
PROGRAMS

Pre compiler
DBA staff Casual users
Parametric
DDL PRIVILEGED Run-time data DML users
STATEMENTS COMMANDS base processor Compiler

DML
Query statements
System A compiler Compiled
DDL E catalog/ (canned)
DML
compiler Data B Compiler Transactions
dictionary Execution
C
Execution Run-time data Execution
base processor
Stored D Concurrency control/Backup/
data manager Recovery sub systems
Stored database

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