01-Oracle 19c-Architecture Overview Oracle

Copyright © 2019, Oracle and/or its affiliates. All rights reserved.
Oracle Database Architecture

2 - 2
Objectives
After completing this lesson, you should be able to:
• List the major architectural components of Oracle
Database
• Explain memory structures
• Describe background processes
• Correlate logical and physical storage structures
• Describe pluggable databases
• Describe ASM storage components

2 - 3
Database (Storage Structures)
Oracle Database Server Architecture: Overview
Server
process
PGA
User
process
Instance
Memory Structures
(System Global Area)
Process Structures
Client
Server

2 - 4
Oracle Database Instance Configurations
D1
D2
I1
I2
I1 I2 I3
D
Clustered System
Nonclustered System
Local Storage
Shared Storage

2 - 5
Connecting to the Database Instance
• Connection: Communication between a user process and
an instance
• Session: Specific connection of a user to an instance
through a user process
SQL> Select …
Session
User
User
process
Server
process
Session
Connection

2 - 6
Oracle Database Memory Structures
Server
process 1
Shared pool
Database
buffer
cache
Streams
pool
Large pool Java pool
Stack
Space
System Global Area (SGA)
Program Global Area (PGA)
Server
process 2
User
Global
Area
Stack
Space
User
Global
Area
PGA
Fixed SGA
Redo log
buffer

2 - 7
Redo log
buffer
Shared pool
Database
buffer
cache
Streams
pool
Shared Pool
• Is a portion of the SGA
• Contains:
– Library cache
— Shared SQL area
– Data dictionary cache
– Server result cache
Shared
SQL Area
Library
Cache
Data Dictionary
Cache
Server Result
Cache
Other
Reserved Pool
Fixed SGA

2 - 8
Shared pool
Database
buffer
cache
Streams
pool
Keep pool
Recycle
pool
nK buffer
cache
Database Buffer Cache
• Is part of the SGA
• Holds copies of data blocks that are read from data files
• Is shared by all concurrent users
Fixed SGA
Redo log
buffer

2 - 9
Redo Log Buffer
• Is a circular buffer in the SGA
• Holds information about changes made to the database
• Contains redo entries that have the information to redo
changes made by operations such as DML and DDL
Shared pool
Database
buffer
cache
Streams
pool
Redo log
buffer
Redo log
buffer
Fixed SGA

2 - 10
Large Pool
Provides large memory allocations for:
• Session memory for the shared server and the Oracle XA
interface
• I/O server processes
• Oracle Database backup and restore operations
Shared pool
Database
buffer
cache
Streams
pool
RECYCLE
buffer pool
Fixed SGA
Redo log
buffer
Large pool
I/O buffer
Response
queue
Request
queue
Free
memory
Parallel
Query
Advanced
Queuing

2 - 11
Java Pool
Java pool memory is used to store all session-specific Java
code and data in the JVM.
Shared pool
Database
buffer
cache
Streams
pool
Java pool
Fixed SGA
Redo log
buffer

2 - 12
Streams Pool
Streams pool memory is used exclusively by Oracle Streams
to:
• Store buffered queue messages
• Provide memory for Oracle Streams processes
Shared pool
Database
buffer
cache
Streams
pool
nK buffer
cache
Redo log
buffer
Streams pool

2 - 13
Program Global Area (PGA)
Server
process 1
Stack
Space
PGA
Shared pool
Database
buffer
cache
Streams
pool
User
Global
Area
User Session
Data
Cursor
State
Sort
Area
Hash
Area
Create Bitmap Area
SQL
Work Areas
Bitmap Merge Area
Fixed SGA
Redo log
buffer

2 - 14
Process Architecture
• User process
– Is the application or tool that connects to the Oracle
database
• Database processes
– Server process: Connects to the Oracle instance and is
started when a user establishes a session
– Background processes: Are started when an Oracle instance
is started
• Daemon / Application processes
– Networking listeners
– Grid Infrastructure daemons

2 - 15
Process Structures
PMON
SMON
Others
Instances (ASM and Database separate)
LREG
ARCn
DBWn LGWR
CKPT
PGA
Background processes
Required:
Optional:
Grid Infrastructure Processes
(ASM and Oracle Restart)
orarootagent
ohas ocssd diskmon
oraagent cssdagent
User
process
Server
process
Listener
RECO MMON MMNL Others

2 - 16
Database Writer Process (DBWn)
Writes modified (dirty) buffers in the database buffer cache to
disk:
• Asynchronously while performing other processing
• To advance the checkpoint
Database buffer
cache
Database Writer
process
Data files
DBWn

2 - 17
Log Writer Process (LGWR)
• Writes the redo log buffer to a redo log file on disk
– When a user process commits a transaction
– When an online redo log switch occurs
– When the redo log buffer is one-third full or contains 1 MB of
buffered data
– Before a DBWn process writes modified buffers to disk
– When three seconds have passed since the last write
• Serves as coordinator of LGnn processes and ensures
correct order for operations that must be ordered
Redo log files
LGWR
Redo log
buffer
LGnn
LGnn

2 - 18
Checkpoint Process (CKPT)
• Records checkpoint information in
– Control file
– Each data file header
• Signals DBWn to write blocks to disk
Checkpoint
process
Data files
Control file
CKPT

2 - 19
System Monitor Process (SMON)
• Performs recovery at instance startup
• Cleans up unused temporary segments
Instance
Temporary
segment
System Monitor
process
SMON

2 - 20
Process Monitor Process (PMON)
• Performs process recovery when a user process fails
– Cleans up the database buffer cache
– Frees resources that are used by the user process
• Monitors sessions for idle session timeout
Process Monitor
process
Database buffer
cache
Failed user process
User
PMON
Server
process

2 - 21
Recoverer Process (RECO)
• Used with the distributed database configuration
• Automatically connects to other databases involved in in-
doubt distributed transactions
• Automatically resolves all in-doubt transactions
• Removes any rows that correspond to in-doubt
transactions
Recoverer process
in database A
In-doubt transaction
in database B
RECO

2 - 22
Listener Registration Process (LREG)
Registers information about the database instance and
dispatcher processes with the Oracle Net Listener
listener
Instance
Memory Structures
(System Global Area)
Process Structures
LREG

2 - 23
Archiver Processes (ARCn)
• Copy redo log files to a designated storage device after a
log switch has occurred
• Can collect transaction redo data and transmit that data to
standby destinations
Archiver process Archive destination
Copies of redo log
files
ARCn

2 - 24
Database Storage Architecture
Online redo log files
Password file
Parameter file Archived redo log
files
Control files Data files
Alert log and trace files
Backup files

2 - 25
Logical and Physical Database Structures
Database
Logical Physical
Tablespace Data file
Segment
Extent
Oracle data
block
Storage System
• SAN
• NAS
• Exadata
• File System
• NFS
• ASM

2 - 26
Segments, Extents, and Blocks
• Segments exist in a tablespace.
• Segments are collections of extents.
• Extents are collections of data blocks.
• Data blocks are mapped to disk blocks.
Segment Extents Data
blocks
Disk blocks
(File System
Storage)

2 - 27
Tablespaces and Data Files
8Kb 8Kb
8Kb 8Kb
8Kb 8Kb
8Kb 8Kb
8Kb 8Kb
8Kb 8Kb
8Kb 8Kb
8Kb 8Kb
Tablespace 1
Data file 1 Data file 2
Extent
64 KB
Extent
64 KB
Segment
128 KB
Tablespace 2 (Bigfile)
Data file 3
Only 1 data file
allowed
<= 128 TB

2 - 28
SYSTEM and SYSAUX Tablespaces
• The SYSTEM and SYSAUX tablespaces are mandatory
tablespaces that are created at the time of database
creation. They must be online.
• The SYSTEM tablespace is used for core functionality (for
example, data dictionary tables).
• The auxiliary SYSAUX tablespace is used for additional
database components.
• The SYSTEM and SYSAUX tablespaces should not be used
for application data.

2 - 29
Multitenant Architecture
Instance
System Global Area
Process Structures
Server
Instance
Multitenant
container
database
root container
Data files Redo Log files
Control files
UNDO
TEMP
SYSTEM
SYSAUX
Seed PDB
Data files
SYSTEM
SYSAUX
SALES PDB
SYSTEM
SYSAUX TBS2
HR PDB
Data files
TEMPO
Data files
TEMP2
PDBid2 PDBid3 PDBid4 PDBid2 PDBid4
All PDBs share:
• Background
processes
• Shared/process
memory
• Oracle metadata
• Redo log files
• Control files
• Undo tablespace

2 - 30
Automatic Storage Management
• Is a portable and high-performance
cluster file system
• Manages Oracle database files
• Manages application files with
ASM Cluster File System (ACFS)
• Spreads data across disks
to balance load
• Mirrors data in case of failures
• Solves storage management
challenges
ASM Cluster
File
System
ASM Dynamic
Volume
Manager
Application
Oracle
Database
Operating system
ASM Files
for Oracle
Database
Automatic Storage Management

2 - 31
ASM Storage Components
Oracle
Database
Data file
ASM allocation
unit
ASM
disk group
ASM disk
ASM file
ASM
extent
File system
ASM

2 - 32
Interacting with an Oracle Database:
Memory, Processes, and Storage
User
PGA
User
process
Server
process
Listener
PMON
SMON Others
Instance
RECO
DBWn LGWR
CKPT
Shared pool
Database
buffer
cache
Streams
pool
Large pool
Java pool
ARCn
Redo log
buffer
Fixed SGA

2 - 33
Quiz
The memory region that contains data and control information
for a server or background process is called:
a. Shared pool
b. PGA
c. Buffer cache
d. User session data

2 - 34
Quiz
What is read into the database buffer cache from data files?
a. Rows
b. Changes
c. Blocks
d. SQL

2 - 35
Quiz
The Process Monitor process (PMON):
a. Performs recovery at instance startup
b. Performs process recovery when a user process fails
c. Automatically resolves all in-doubt transactions
d. Writes the redo log buffer to a redo log file

2 - 36
Summary
In this lesson, you should have learned how to:
• List the major architectural components of Oracle
Database
• Explain memory structures
• Describe background processes
• Correlate logical and physical storage structures
• Describe pluggable databases
• Describe ASM storage components

01-Oracle 19c-Architecture Overview Oracle

Recommended

More Related Content

Similar to 01-Oracle 19c-Architecture Overview Oracle (20)

Recently uploaded (20)

01-Oracle 19c-Architecture Overview Oracle