The document discusses the role and functions of database buffers and buffer managers. It states that a database buffer is a temporary storage area in memory used to hold copies of database blocks from disk. The buffer manager is responsible for bringing pages from disk into the buffer pool in memory as needed. It manages the buffer pool, which divides main memory into pages called frames to cache data and minimize disk access. The buffer manager controls data access between memory and disk to improve database performance.

1. M.Rajshree
II-MSC(IT)
Nadar saraswathi college of arts&science

2.  Database management system is a software
which is used to manage the database. For
example: my sql, oracle, etc are a very
popular commercial database which is used in
different applications
 DBMS provides an interface to perform
various operations like database creation,
storing data in it, updating data, creating a
table in the database

3.  Database is stored in disk
 For read and write database operation must
reside in memory
 A database buffer is a temporary storage area
in memory used to hold a copy of
a database block.
 DBMS application programs require
input/output (I/O) operations which are
performed by a component of operating
system

4.  The buffer manager is the software layer
that is responsible for bringing pages from
physical disk to main memory as needed
 The buffer manages the available main
memory by dividing the main memory into a
collection of pages, which we called
as buffer pool.
 Database buffers are grouped in an area of
memory called the buffer pool

5.  The main memory pages in the buffer pool
are called frames
 A buffer pool is an area of main memory that
has been allocated by the database manager
 Buffer manager is used to allow processes to
get memory they need while minimizing the
delay.

6.  Data must be in RAM for DBMS to
operate on it
 Buffer manager hides the fact that not all
data is in RAM
 Buffer manager controls main memory
directly
 The subsystem responsible for the
allocation of buffer space is called
the buffer manager

7.  Buffer manager allocates buffer in virtual
memory allowing os to decide how to use
buffer
 If a program performs reading from existing
buffers similarly if a program performs an
output statement: it calls the buffer manager
for output operation - to satisfy the requests
by writing to the buffers

8.  The purpose of buffer pools is to cache table
and index data from disk all databases have
their own buffer pools
 A default buffer pool is created at the time of
creation of new database
 The pages in the buffer pool which are
updated with data but are not written onto
the disk are called “Dirty” pages

9.  Each table space is associated with a
specific buffer pool in a database.
 One table space is associated with one
buffer pool.
 The size of buffer pool and table space
must be same.

10.  Multiple buffer pools allow you to configure
the memory used by the database to increase
its overall performance.

11. Thank you