les_01_arch_presentation_asm_oracle_rac_

Copyright © 2007, Oracle. All rights reserved.
Database Architecture and ASM

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Objectives
After completing this lesson, you should be able to:
• Describe the Oracle Database architecture
• Describe Automatic Storage Management (ASM)
• Set up initialization parameter files for ASM and database
instances
• Start up and shut down ASM instances
• Administer ASM disk groups

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The Oracle Database
The Oracle Relational Database Management System
(RDBMS) is a database management system that provides an
open, comprehensive, integrated approach to information
management.

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Database
Data files
Online redo
log files
Control
files
Oracle Database Architecture: Overview
Database
buffer
cache
Shared pool
Data dictionary
cache
Library
cache
PMON
SMON Others
Server
process
PGA
Archived
log files
User
process
Instance
ARCn
SGA
DBWn
Redo log
buffer
LGWR
CKPT

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Connecting to the Database
• 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
Connection
USER
User

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Database
Oracle Database Server Structures
PMON
SMON Others
Data files
Online redo
log files
Control
files
Instance
ARCn
DBWn LGWR
CKPT
Storage structures
User
process
Server
process
Memory structures
Processes
Database
buffer
cache
Shared pool
Data dict.
cache
Library
cache
SGA
Redo log
buffer

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Oracle Memory Architecture
SGA
Database buffer
cache
Redo log
buffer
Java
pool
Streams
pool
Shared pool
Large pool
PGA PGA PGA
Background
process
Server
process 1
Server
process 2
Shared
SQL area
Library
cache
Data Dictionary
cache
Other
I/O Buffer
Response
queue
Request
queue
Free
memory

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Process Architecture
• User process:
– Is started when a database user or a batch process connects
to 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
PMON
SMON Others
Instance
ARCn
DBWn LGWR
CKPT
PGA
User
process
Server
process Background processes
Database
buffer
cache
Shared pool
Data dictionary
cache
Library
cache
SGA
Redo log
buffer

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Process Structures
…Server n
processes
SGA
…Oracle
background
processes
PMON SMON Others
RECO ARCn
DBWn LGWR
CKPT
Server Server
Server
Server Server
Database
buffer
cache
Shared pool
Data dict.
cache
Library
cache
SGA
Redo log
buffer

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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

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Logical and Physical Database Structures
Database
Logical Physical
Tablespace Data file
OS block
Segment
Extent
Oracle data
block
Schema

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Tablespaces and Data Files
• Tablespaces consist of one or more data files.
• Data files belong to only one tablespace.
USERS tablespace
Data file 1 Data file 2

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SYSTEM and SYSAUX Tablespaces
• The SYSTEM and SYSAUX tablespaces are mandatory
tablespaces.
• They are created at the time of database creation.
• The SYSTEM tablespace is used for core functionality (for
example, data dictionary tables).
• The auxiliary SYSAUX tablespace is used for additional
database components (such as the Enterprise Manager
Repository).

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Segments, Extents, and Blocks
• Segments exist within a tablespace.
• Segments are made up of a collection of extents.
• Extents are a collection of data blocks.
• Data blocks are mapped to disk blocks.
Segment Extents Data
blocks
Disk
blocks

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Database Architecture:
Summary of Structural Components
• Memory structures:
– System Global Area (SGA): Database buffer cache, redo
buffer, and various pools
– Program Global Area (PGA)
• Process structures:
– User process and server process
– Background processes: SMON, PMON, DBWn, CKPT,
LGWR, ARCn, and so on
• Storage structures:
– Logical: Database, schema, tablespace, segment, extent, and
Oracle block
– Physical: data files, control files, and redo log files

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Automatic Storage Management:
Review
• Portable and high-performance cluster file system
• Manages Oracle database files
• Data spread across disks
to balance load
• Integrated mirroring across
disks
• Solves many storage
management challenges
ASM
File
system
Volume
manager
Operating system
Application
Database

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ASM: General Architecture
ASM
instance
SID=+ASM
ASM disks ASM disks
ASM disk group 1
DB instance
SID=SALES
ASMB
RBAL
ARB0
ARBA
…
ASM disks ASM disks ASM disks
ASM disk group 2
ASM disks
DBW0
RBAL
FG
GMON

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Creating an ASM Instance

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ASM Instance Initialization Parameters
INSTANCE_TYPE = ASM
DB_UNIQUE_NAME = +ASM
ASM_POWER_LIMIT = 1
ASM_DISKSTRING = '/dev/rdsk/*s2', '/dev/rdsk/c1*'
ASM_DISKGROUPS = dgroupA, dgroupB
SPFILE = '+DATA/ORCL/orclspfile.ora_1'

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Starting Up an ASM Instance
$ export ORACLE_SID='+ASM'
$ sqlplus /nolog
SQL> CONNECT / AS sysasm
Connected to an idle instance.
SQL> STARTUP;
Total System Global Area 284565504 bytes
Fixed Size 1299428 bytes
Variable Size 258100252 bytes
ASM Cache 25165824 bytes
ASM diskgroups mounted

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SYSASM Role
• SYSASM role to manage ASM instances avoids overlap
between DBAs and storage administrators
• For ASM instances, SYSDBA will be deprecated in the future:
– Oracle Database 11g Release 1 behaves as in 10g
– In future releases SYSDBA privileges restricted in ASM
instances
SQL> CONNECT / AS SYSASM
SQL> CREATE USER ossysasmusername IDENTIFIED by passwd;
SQL> GRANT SYSASM TO ossysasmusername;
SQL> DROP USER ossysasmusername;
SQL> CONNECT ossysasmusername / passwd AS SYSASM;

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Accessing an ASM Instance
Disk group Disk group
Storage system
As SYSASM
or SYSDBA
As SYSOPER
ASM
instance
All operations Limited
operations

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Using Enterprise Manager to Manage ASM Users

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Shutting Down an ASM Instance
SHUTDOWN NORMAL
ASM instance
Database instance A Database instance B
1 1
2
3

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ASM Storage: Concepts
Database
Tablespace
Segment
Extent
Oracle
block
Data file
Physical
block
ASM
disk group
ASM disk
ASM file
Allocation unit
File-system
file
or
raw device

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ASM Disk Group
• Is a pool of disks managed as a logical unit
• Partitions total disk space into
uniform sized units
• Spreads each file evenly
across all disks
• Uses coarse- or fine-grain striping
on the basis of file type
• Administers disk groups, not files
Disk group
ASM
instance

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Failure Group
Controller 1 Controller 2
Failure group 1 Failure group 2
Disk group A
Controller 3
Failure group 3
1 7 13
1 7 13
1 7 13
1 7 13
1 7 13
1 7 13
1 7 13
1 7 13
1 7 13
2
3
4
5
6

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Disk Group Mirroring
• Mirror at AU level
• Mix primary and mirror
AUs on each disk
• External redundancy:
Defers to hardware
mirroring
• Normal redundancy:
– Two-way mirroring
– At least two failure groups
• High redundancy:
– Three-way mirroring
– At least three failure groups

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Disk Group Dynamic Rebalancing
• Automatic online
rebalance whenever
storage configuration
changes
• Only move data
proportional to
storage added
• No need for manual
I/O tuning
• Online migration to
new storage
• Configurable load
on system using ASM_POWER_LIMIT

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Managing Disk Groups
CREATE DISKGROUP
ALTER DISKGROUP
DROP DISKGROUP
ASM
instance
Database
instance

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Creating and Dropping Disk Groups
CREATE DISKGROUP dgroupA NORMAL REDUNDANCY
FAILGROUP controller1 DISK
'/devices/A1' NAME diskA1 SIZE 120G FORCE,
'/devices/A2',
'/devices/A3'
FAILGROUP controller2 DISK
'/devices/B1',
'/devices/B2',
'/devices/B3';
DROP DISKGROUP dgroupA INCLUDING CONTENTS;

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Adding Disks to Disk Groups
ALTER DISKGROUP dgroupA ADD DISK
'/dev/rdsk/c0t4d0s2' NAME A5,
'/dev/rdsk/c0t7d0s2' NAME A8;
ALTER DISKGROUP dgroupA ADD DISK '/devices/A*';
Disk formatting
Disk group rebalancing

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ASM Disk Group Compatibility
• Compatibility of each disk group is separately controllable:
– ASM compatibility controls ASM metadata on-disk structure
– RDBMS compatibility controls minimum consumer client level
– Useful with heterogeneous environments
• Setting disk group compatibility is irreversible.
DB
instance
COMPATIBLE.RDBMS
COMPATIBLE
ASM disk
group
>=
<=
COMPATIBLE.ASM
ASM
instance
<= COMPATIBLE

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ASM Disk Group Attributes
Name Property Values Description
au_size C 1|2|4|8|16|32|64MB Size of allocation units in the disk group
compatible.rdbms AC Valid database version Format of messages exchanged between DB
and ASM
compatible.asm AC Valid ASM instance version Format of ASM metadata structures on disk
disk_repair_time A 0 M to 232 D Length o time before removing a disk once
OFFLINE
template.tname.
redundancy
A UNPROTECT|MIRROR|HIGH Redundancy of specified template
template.tname.
stripe
A COARSE|FINE Striping attribute of specified template
CREATE DISKGROUP DATA NORMAL REDUNDANCY
DISK '/dev/raw/raw1','/dev/raw/raw2'
ATTRIBUTE 'compatible.asm'='11.1';
C: CREATE
A: ALTER

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Using Enterprise Manager to
Edit Disk Group Attributes

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Miscellaneous ALTER Commands
Remove a disk from dgroupA:
Add and drop a disk in a single command:
Cancel a disk drop operation:
ALTER DISKGROUP dgroupA DROP DISK A5;
ALTER DISKGROUP dgroupA
DROP DISK A6
ADD FAILGROUP fred
DISK '/dev/rdsk/c0t8d0s2' NAME A9;
ALTER DISKGROUP dgroupA UNDROP DISKS;

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ASMCMD Utility
$ export ORACLE_SID=+ASM
$ asmcmd
ASMCMD> ls -l DGROUP1/ORCL/DATAFILE
Type Redund Striped Time Sys Name
DATAFILE MIRROR COARSE OCT 05 21:00:00 Y HRAPPS.257.570923611
DATAFILE MIRROR COARSE OCT 05 21:00:00 Y TBSASM.256.570922917
ASMCMD>
SQL> CREATE TABLESPACE tbsasm DATAFILE '+DGROUP1' SIZE 100M;
Tablespace created.
SQL> CREATE TABLESPACE hrapps DATAFILE '+DGROUP1' SIZE 10M;
Tablespace created.

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ASMCMD Utility
$ asmcmd help
md_backup
md_restore
lsdsk
full
nodg
newdg
User created directories
Templates
Disk group compatibility
Disk group name
Disk names and failure groups
ASMCMD> md_backup –b /tmp/dgbackup070222 –g admdsk1 –g asmdsk2
ASMCMD> md_restore –t full –g asmdsk1 –i backup_file
ASMCMD> lsdsk -k DATA *_0001
repair/remap

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ASM Scalability and Performance
• Extent size grows automatically according to file size.
• ASM support variable extents size to:
– Raise maximum possible file size
– Reduce memory utilization in shared pool
• ASM imposes the following limits:
– 63 disk groups in a storage system
– 10,000 ASM disks in a storage system
– 4 petabyte maximum storage for each ASM disk
– 40 exabyte maximum storage for each storage system
– 1 million files for each disk group

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Summary
In this lesson, you should have learned how to:
• Describe the Oracle Database architecture
• Describe Automatic Storage Management (ASM)
• Set up initialization parameter files for ASM and database
instances
• Start up and shut down ASM instances
• Administer ASM disk groups

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Practice 1 Overview:
Database Architecture and ASM
This practice covers the following topics:
• Creating and starting an ASM instance
• Creating and using ASM disk groups
• Managing an ASM instance
• Dynamic disk group rebalancing

les_01_arch_presentation_asm_oracle_rac_

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