Oracle Architecture and Metrics
Here is an illustrated Nutshell FAQ on Oracle explained in-depth using a hands-on approach and constructivist sequence. This crystalizes stacks of books, several classes, thousands of user group entries, and years of hard-won experience.

Topics this page ... Authorization Methods Background Processes Catalog.sql Checkpoint Process (CKPT) Clusters in Tables Control Files Datafiles Data Dictionary Views DSS (Decision Support System) Enqueues Extents Fragmentation Instances Latches Library Cache Log Writer (LGWR) Memory areas OLTP (On-Line Transaction Processing) Packages Parameter File Password Files Performance Views Process Monitor (PMON) Program Global Area (PGA) Processes RMAN Redo Logs Rollback Segments Sequences SID (System Identifier) Shared Pool Shared SQL Pool Sorting Synonyms Server Services Server Manager utility System Global Area (SGA) System Monitor (SMON) Triggers Views

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Oracle's Documentation home page (tahiti.oracle.com)

Overview: Architecture Core Components

The Oracle Database Management System (DBMS) consists of several components (loosely similar to UNIX's implementation of the multitasking operating system):

Oracle core software and scripts installed in the folder specified in $ORACLE_HOME environment variable and in Windows Registry.
Clients establishing sessions connecting to user applications by going through interfaces using Protocols.
“Databases” have two parts:
- Instances (the “brain" of the system) provide the capability of accessing stored data. Each instance consists of:
  - data files in static storage devices,
  - memory areas in RAM used by
  - background processes servicing requests and user applications
Development and Query Tools managing the DBMS such as the Enterprise Manager and The Database configuration Assistant (DBCA); and

Topics this page:

Logical Data Structures

Physical Data Structures

Initialization Procs

Memory Architecture

Your comments???

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Installation

Oracle Installation Products

Where Is Oracle Installed?

Version	OS	Installer Setup File	Installer MB	ORACLE_BASE	ORACLE_HOME
10.2.0.1	Express Edition on Windows XP	OracleXEUniv.exe	211,849	C:\oraclexe	\product\10.2.0\server
10.2.0.1	Enterprise Edition Windows 32bit	10201_database_win32.zip	639,674	C:\oracle\product\10.2.0	\db_1

Reviewing Installed Starter Database Contents

Other

OS Environment Variables For Where Oracle Is Installed

When Oracle Personal Express Edition (XE) is installed, it creates by default folder C:\oraclexe with the folders in the table.
Create OS environment variable ORACLE_BASE to hold value "C:\oraclexe".

Different installers use other drive/folder paths.

Envrionment variables enable the root path to be referenced by $ORACLE_BASE within Unix and %ORACLE_BASE% within Windows. For example, within Windows, the file created to detail installation activities can be found at "%ORACLE_BASE%\app\oracle\admin\xe\bdump\alert_xe.log" Copy and paste this on the address bar of Windows Explorer.

"xe" is the database Instance Identifier (SID) for Express Edition.
"orcl" is the default db_name value in INIT.ORA for the Enterprise Edition.
Create OS environment variable ORACLE_SID to hold SID value "xe" or the instance SID value for your application.

The path to executables (exe and dll files) within the bin folder containing Oracle supplied command line utilities for a Oracle version is stored within OS environment variable $ORACLE_HOME in Unix.

On Windows machines, rather than setting a %ORACLE_HOME% environment variable, Oracle uses the path in Windows Registry key HKEY_LOCAL_MACHINE/SOFTWARE/ORACLE using the Regedit utility

Oracle 11g only requires user specification of ORACLE_BASE, since it creates ORACLE_HOME from it.

Change OS Environment variable PATH to replace the path with variable %ORACLE_HOME%/bin where Oracle executables run from whatever is the current folder. Remember the $ prefix in UNIX and two % in Windows. Since it's a variable, PATH does not need to be changed when the Oracle path needs to change.

To change from using Oracle 10g to Oracle 11g on the same machine, change the value of ORACLE_HOME.

To connect to a network different than the one active while Oracle was installed, change in ...\db_1\NETWORK\ADMIN\listener.ora the default port from 1521 to 1525.

Express Edition Files Installed

app/oracle	admin/XE	adump bdump cdump dpdump pfile udump
	doc flash_recovery_area/XE/ONLINELOG
	product\10.2.0\server *(ORACLE_HOME)*	bin etc.
oradata/XE	CONTROL.DBF SYSAUX.DBF SYSTEM.DBF TEMP.DBF UNDO.DBF USERS.DBF

Enterprise Edition Files Installed

admin/orcl	adump bdump cdump dpdump pfile udump
db_1 *(ORACLE_HOME)*	bin etc.
flash_recovery_area/orcl/ONLINELOG
oradata/orcl	CONTROL01.DBF CONTROL02.DBF CONTROL03.DBF REDO01.DBF REDO02.DBF REDO03.DBF SYSAUX01.DBF SYSTEM01.DBF TEMP01.DBF UNDOTBS01.DBF USERS01.DBF

The default SAP installation names Oracle datafiles with a prefix which matches its tablespace name. Rather than the dbf filename suffix, SAP requires datafiles to have names such as "psappooli.data3" for the third datafile for the SAP POOL data indexes.

Background Services/Processes

Service Name	Startup	Bin	Notes
OracleServiceXE OracleServiceORCL	Automatic	ORACLE.EXE XE	Oracle RDBMS Kernel Executable background process (runs multi-threaded). Unlike UNIX ports of Oracle Database 10g, Oracle Database 10g on Windows is implemented as a single operating system process.
OracleXEClrAgent	Manual	OraClrAgnt.exe	CLR agent (XE Edition only)
OracleXETNSListener OracleOraDb10g_home1TNSListener	Automatic	tnslsnr.exe	"Transparent Network Substrate" (Oracle Network Service) Listener
OracleOraDb10g_homeiSQL*Plus	Automatic	isqlplussvc.exe	iSQL *Plus Application Server (Enterprise edition only)
OracleMTSRecoveryService	Automatic	omtsreco.exe	MTS Recovery Service
OracleMJobSchedulerXE OracleMJobSchedulerORCL	Disabled	extjob.exe XE	Job Scheduler
OracleDBConsoleord	Automatic	nmesrvc.exe	(Enterprise edition only)

Oracle 10g takes VM Size of 651,540K.

A different service name is assigned to process each instance. Service names contain "XE" for Express Edition, or "ORCL" or "OraDb10g_home1" automatically assigned by the Enterprise edition installer.

Statup is "Automatic" when that the service starts every time Windows boots up.
Statup is "Manual" if that service does not start with Windows boots up and requires manual intervention to start.

Executables for running services and the dll files they use (oraclient10.dll, etc. also in the same bin folder) cannot be deleted (to uninstall Oracle) until their service is stopped.

Oracle Enterprise Components

Advanced Database architectures include: Oracle Managed Files (OMF) to automate creation and dropping of datafiles and management of redo log and control files; Partitioning of tables by range, list, hash, composition; Replication (not suited to failover and backup); Standby (Failover) Databases, Grid Computing, which consists of OEM Grid Control of Oracle RAC (Real Application Clusters) and Oracle 10g platform. independent Cluster Ready Services (CRS) to handle failover of services to surviving nodes

ASM, Transportable Tablespaces, Streams, Scheduler.

Oracle features for a grid computing architecture: 朞racle Real Application Clusters (RAC) 朅utomated Storage Management (ASM) 朞racle Transportable Tablespaces 朞racle Streams 朞racle Scheduler 朞racle Enterprise Manager Grid Control<!--

Service	Startup	Bin	Notes
OracleOraDb10g_homeiSQL*Plus	Automatic	isqlplussvc.exe	iSQL *Plus Application Server
OracleXEClrAgent	Manual	OraClrAgnt.exe	CLR agent
OracleXETNSListener	Automatic	tnslsnr.exe	"Transparent Network Substrate" (Oracle Network Service) Listener
OracleMTSRecoveryService	Automatic	omtsreco.exe	MTS Recovery Service
OracleMJobSchedulerXE	Disabled	extjob.exe XE	Job Scheduler
OracleOraHomeXXAgent	Automatic	-	-
OracleOraHomeXXClientCache	Manual	-	-
OracleOraHomeXXCMAdmin	Manual	-	-
OracleOraHomeXXCMan	Manual	-	-
OracleOraHomeXXDataGatherer	Automatic	-	-
OracleOraHomeXXHTTPServer	Automatic	-	The Apache web server defaults to serve pages from X:\ oracle\ oraXX\ Apache\ Apache\ htdocs\ index.html
OracleOraHomeXXPagingServer	Manual	-	-

Partitioning Option
Advanced Networking Option for network security using encryption and data integrity checking with enhanced user authentication services.
Objects Option - Bit-mapped Indexes
Parallel Server Option - Parallel Query, DML, Index Scans, Index Build
Enterprise Manager Performance Pack -- six applications for advanced diagnostics, monitoring and tuning of Oracle databases
Advanced Queuing
Advanced Replication
Incremental and Parallel Backup and Recovery
Point-in-time Tablespace Recovery

Starting Oracle Services

If Oracle Windows Express Edition (XE) has been installed

ORACLE_HOME/bin

OracleService...

...TNSListener

If the Oracle Enterprise Edition was installed it is assumed that the database just runs.

Initialization with SPFILE or PFILE (INIT.ORA)

initialization parameters

pfile

SID

Since Oracle reads the pfile only when it starts, changes to it (using a Notepad or other text editor) requires the databse to be restarted.

Oracle 10g added a way to change init parameter values dynamically (while the database is running):

ALTER SESSION set  parameter = value ;
ALTER SYSTEM set  parameter = value  SCOPE = SPFILE;

Oracle 10g introduced the spfile (server parameter file) named spfileSID.ora to retain parms so that they can be applied the next time the database starts.

Dynamic changes to parameters can also be made by Oracle's autotune intelligence.

Since the spfile is open for update as the database runs, it can't be edited like the pfile can. But the spfile can be backed-up to a pfile with a command like:

create pfile=/path/to/backup.ora from spfile;

Oracle 10g by default looks for a spfile. But if a spfile can't be found, Oracle looks for the pfile (as before).

When the database is restarted using spfile, the DBA must login again with proper privileges.

<!-- Freeman, R. and Karam, S. (2006). Oracle concepts

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Oracle Architecture and Metrics

Overview: Architecture Core Components

Installation

Oracle Installation Products

Where Is Oracle Installed?

OS Environment Variables For Where Oracle Is Installed

Express Edition Files Installed

Enterprise Edition Files Installed

Background Services/Processes

Oracle Enterprise Components

Starting Oracle Services

Initialization with SPFILE or PFILE (INIT.ORA)

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