Oracle Database Buffer Cache management. How can we monitor and how to manage it.

1. How Buffer Cache
Working in Oracle?
Buffer Cache
Management

2. A buffer cache is a portion of memory used to
temporarily hold data from storage devices for
quicker access.
It stores frequently accessed data to improve
the performance of reading and writing data.
It includes free buffers, pinned buffers, dirty
buffers, and the least recent use chain.
INTRODUCTION TO BUFFER CACHE IN ORACLE
Definition of buffer cache

3. The buffer cache helps improve performance by reducing the need to constantly read from and
write to the disk.
Free buffers are available for new data, pinned buffers are currently being used and cannot be
replaced, and dirty buffers need to be written back to the disk.
Checkpoints ensure that all modified data is written to the storage device, maintaining data
integrity.
INTRODUCTION TO BUFFER CACHE IN
ORACLE
Importance of buffer cache in database management

4. Free buffers are available for
new data to be read into.
Pinned buffers are currently
being used and cannot be
replaced.
Dirty buffers have been
modified and need to be
written back to the disk.
INTRODUCTION TO BUFFER CACHE IN ORACLE
Overview of different types of buffers (free, pinned,
dirty)

5. The least recent use chain tracks the order in
which buffers are accessed.
It identifies the least recently used buffer for
replacement when needed.
This optimises memory usage and
performance in the system.
BUFFER REPLACEMENT AND MANAGEMENT
Explanation of least recent
use chain

6. Buffer replacement is
managed through free,
pinned, and dirty buffers.
The system looks for free
buffers first and then
considers replacing from
the least recent use chain.
Periodic checkpoints ensure
that dirty buffers are written
to disk to free up space for
new data.
BUFFER REPLACEMENT AND
MANAGEMENT
How buffer replacement is managed

7. Buffer Replacement and Management
Impact of buffer replacement on system performance
Buffer replacement can
significantly affect data
retrieval and processing
speed and efficiency.
A large number of dirty
buffers during a
checkpoint can slow
down system
performance.
The use of the least
recent use chain for
buffer replacement
directly impacts overall
system performance.

8. To ensure all modified (dirty) buffers are written to disk
Reducing the risk of data loss in the event of a system failure
Maintaining data integrity and consistency
Freeing up dirty buffers for reuse
CHECKPOINT MECHANISM
Purpose of checkpoint in buffer cache

9. Using the checkpoint process to flush all dirty buffers to disk
Preventing overwriting of modified buffers before writing to disk
Utilizing pinned buffers to safeguard modified buffers
Reducing the number of dirty buffers for efficient recovery
CHECKPOINT
MECHANISM
Ensuring all modified buffers are written to
disk

10. Reducing the amount of work needed for recovery after a system failure
Minimizing the number of dirty buffers for efficient recovery
Maintaining database consistency by writing data from buffer cache to database
files
Facilitating restoration of the database to a consistent state after a system failure
CHECKPOINT MECHANISM
Effect of checkpoint on database consistency and
recovery

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