Oracle DB
Architecture
Simon Huang
simon581923@gmail.com

Agenda
• 基本架構
• 資料庫引擎架構
• RAC(Real Application Clusters)架構

參考文件
• Oracle Database Documentation Library
 http://www.oracle.com/pls/db112/homepage
• E10897
 Oracle Database 2 Day DBA 11g Release 2 (11.2)
• E17264
 Oracle Database 2 Day + Real Application Clusters Guide 11g Release 2
(11.2)

基本架構

以Instance為基礎
DB1
DB2
DB3
Instance1
Instance2
Instance3
DBnInstancen

Instance
• In Windows
 Services
• In Unix-like
 Processes

比較詳細的Oracle DB結構

資料庫引擎架構

基本Instance概觀

Background Processes
• Database writer (DBWRn)
 The database writer writes modified blocks from the database buffer cache to the
files on a disk.
 Oracle Database allows a maximum of 36 database writer processes.
• Log writer (LGWR)
 The log writer process writes redo log entries to disk.
 Redo log entries are generated in the redo log buffer of the System Global Area
(SGA) and the log writer process writes the redo log entries sequentially into an
online redo log file.
• Checkpoint (CKPT)
 At specific times, all modified database buffers in the SGA are written to the data
files by a DBWR.
 The checkpoint process signals DBWRn, updates the data files and control files of
the database, and records the time of this update.
• System monitor (SMON)
 The system monitor performs instance recovery when a failed instance is
restarted.
• Process monitor (PMON)
 The process monitor performs a recovery when a user process fails.
 It cleans up the cache and frees resources that the failed process was using.

Other Background Processes
• Archiver (ARCn)
 Archiver processes copy the online redo log files to archival
storage when the log files are full or a log switch occurs.
• Manageability monitor (MMON)
 This process performs various management-related
background tasks, for example:
 Issuing alerts whenever a given metric violates its threshold value
 Taking snapshots by spawning additional processes
 Capturing statistical values for SQL objects that have been
recently modified
• Job Queue Processes (CJQ0 and Jnnn)
 Job queue processes run user jobs, often in batch mode. A job
is a user-defined task scheduled to run one or more times.

System Global Area(SGA)
• Database buffer cache
 Before data stored in the database can be queried or modified, it
must be read from a disk and stored in the buffer cache.
 All user processes connected to the database share access to the
buffer cache.
 For optimal performance, the buffer cache should be large enough
to avoid frequent disk I/O operations.
• Shared pool
 SQL statements that can be reused
 Information from the data dictionary such as user account data,
table and index descriptions, and privileges
 Stored procedures, which are executable code that is stored in the
database
• Redo log buffer
 This buffer improves performance by caching redo information
until it can be written to the physical online redo log files stored
on disk.

Other SGA Component
• Result cache
 The result cache buffers query results.
 If a query is run for which the results are stored in the result
cache, then the database returns the query results from the
result cache.
 This SGA component speeds the execution of frequently run
queries.
• Large pool
 This optional area is used to buffer large I/O requests for various
server processes.
• Java pool
 The Java pool is an area of memory that is used for all session-
specific Java code and data within the Java Virtual Machine
(JVM).
• Streams pool
 The Streams pool is an area of memory that is used by the Oracle
Streams feature

Program Global Area(PGA)
• A Program Global Area (PGA) is a memory area used by a
single Oracle Database server process.
• When we connect to an Oracle database instance, we create
a session that uses a server process for communication
between the client and database instance.
• Each server process has its own PGA.
• The PGA is used to process SQL statements and to hold
logon and other session information.
• The amount of PGA memory used and the contents of the
PGA depend on whether the instance is running in
dedicated server or shared server mode.
• The total memory used by all individual PGAs is known as
the total instance PGA memory, or instance PGA.
• Setting the size of the instance PGA in Database Control
Files, not individual PGAs.

Detail View of 11g

Detail View of 12c

Real Application
Clusters(RAC)

基本架構

RAC基本系統需求
• Clustering OS
 Windows Server Enterprise Edition, 啟用Cluster服務
 Unix-like，安裝啟用Cluster套件
• Oracle Grid Infrastructure
 Oracle Automatic Storage Management(ASM)
 Oracle Clusterware
• Server Hardware (for each node)
 Physical memory (at least 1.5 gigabyte (GB) of RAM)
 An amount of swap space equal to the amount of RAM
 Temporary space (at least 1 GB) available in /tmp
 All servers that are used in the cluster must have the same chip
architecture, for example, all 32-bit processors or all 64-bit
processors
• Oracle Universal Installer verifies that your server and
operating system meet the listed requirements.

Shared Storage需求
• SAN or NAS
• Fiber Channel or iSCSI and Logical Unit Number(LUN)
• RAID 5, 6 or 10
• At least 5.5 GB of available disk space for
 The Grid home directory
 The binary files for Oracle Clusterware, Oracle Automatic
Storage Management (Oracle ASM) and their associated log
files
• At least 4 GB of available disk space for the Oracle
Database home directory, or Oracle home directory.
• Oracle ASM

Network Hardware需求
• Each node must have at least two network interface cards (NIC).
• One adapter is for the public network interface and the other adapter is
for the private network interface (the interconnect).
• For Public interface
 The names must be the same for all nodes.
 Support TCP/IP.
• For Private interface
 The names must be the same for all nodes as well.
 Support the user datagram protocol (UDP).
 Using high-speed network adapters and a network switch(Gigabit Ethernet or
better).
 Supports TCP/IP
 Every node in the cluster must be able to connect to every private network
interface in the cluster.
• The host name of each node must conform to the RFC 952 standard,
which permits alphanumeric characters.
• Host names using underscores ("_") are not allowed.

IP Address需求
• GNS virtual IP address (GNS installations only)
 GNS: Grid Naming Service
• Single Client Access Name (SCAN)
• Virtual IP address
• Public IP address
• Private IP address

RAC Example (Simple)

RAC Example (Complex)

Tools for Oracle Clusterware,
ASM and RAC
• Oracle Universal Installer (OUI)
• Cluster Verification Utility (CVU)
 OUI runs CVU after the Oracle Clusterware installation to verify your
environment.
• Oracle Enterprise Manager
• SQL*Plus
• Server Control (SRVCTL)
• Cluster Ready Services Control (CRSCTL)
• Database Configuration Assistant (DBCA)
• Oracle Automatic Storage Management Configuration Assistant
(ASMCA)
• Oracle Automatic Storage Management Command Line utility
(ASMCMD)
• Listener Control (LSNRCTL)

Q & A