DB MANAGER-DAY8

DBMS Components

· File manager

· Database manager

· Query processor

· DML precompiler

· DDL compiler

Database Manager :

The database manager is the program or program unit that provides the interface between the physical level and the conceptual level.

Functions of the database manager:

· Interaction with the file manager (file system)

· Minimizing file reads and writes, as disk access is slower than main memory acces

· Translating DML commands to file operations

· Integrity enforcement

· checking that consistency constraints are satisfied

· taking some action when they aren't

· Security enforcement

· Preventing unathorized access to data

· Example: through a password and security classification system

· Backup and recovery

· Detect when information in the database or data dictionary is lost or corrupted due to disk crash, power failure, software errors ...

· Restore the database to a previous consistent state

· Concurrency control - making sure that concurrent updates don't give surprising or inconsistent results.

The database manager for a small system typically does not implement all of these functions.