This document provides an overview of Oracle Automatic Storage Management (ASM). It describes ASM's architecture and components, including ASM instances, disk groups, disks, files, and utilities for managing ASM. Key benefits of ASM include striping files across disks for load balancing, mirroring for redundancy, and features like online disk reconfiguration and dynamic rebalancing.

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ASM Overview

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Objectives
After completing this lesson, you should be able to describe the following:
• Automatic Storage Management (ASM) architecture
• Components of ASM

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What Is Oracle ASM?
Application
Operating system
Hardware
Logical Volume Manager
File system
Application
Operating system
Hardware
ASM

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Oracle ACFS
• Multi-platform, Scalable file system, and storage management technology that extends
Oracle ASM functionality
• Support Oracle database
files and other files.
• Spreads data across
disks to balance load.
• Provides integrated mirroring
across disks.
ASM/ADVM
3rd Party FS
Operating System
ACFS
Oracle ASM
Files for Oracle
Database
Application
Oracle ASM
Oracle RAC Application

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ASM Features and Benefits
• Stripes files rather than logical volumes
• Provides redundancy on a file basis
• Enables online disk reconfiguration and dynamic rebalancing
• Significantly reduces the time to resynchronize a transient failure by tracking changes
while the disk is offline
• Provides adjustable rebalancing speed
• Is cluster-aware
• Supports reading from mirrored copy instead of primary copy for extended clusters
• Is automatically installed as part of Grid Infrastructure

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ASM Software Installation
• Oracle ASM is installed as part of an Oracle Grid Infrastructure installation either for a
standalone cluster or for a standalone server.
• Oracle ASM is installed in the Oracle Grid Infrastructure home before Oracle Database
is installed in a separate Oracle home.
• Oracle ASM is integrated with Oracle Clusterware.
• Oracle Clusterware or Oracle Restart is responsible for:
– Starting and stopping ASM instances
– Mounting and dismounting disk groups
– Enabling and disabling ACFS volumes
– Starting and stopping dependent database instances

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Understanding Oracle ASM Concepts
The key components of Oracle ASM include:
• Oracle ASM Instances
• Oracle ASM Disk Groups
• Mirroring and Failure Groups
• Oracle ASM Disks
• Oracle ASM Allocation Units
• Oracle ASM Files

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ASM Components: ASM Instance
The ASM instance comprises the process and memory components for ASM.
System Global Area (SGA) – memory
Shared
pool
Large
pool
ASM
cache
Free
memory
ASM instance
Other misc. processes
Processes – CPU components
RBAL ARBn GMON Onnn PZ9n
MARK

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ASM Instance Primary Processes
The primary processes of an ASM instance are responsible for the ASM-related activities.
Process Description
RBAL Opens all device files as part of discovery and coordinates the rebalance activity
ARBn Refers to one or more slave processes that perform the rebalance activity
GMON Is responsible for managing disk-level activities such as drop or offline and advancing ASM disk
group compatibility
MARK Marks ASM allocation units as stale following a missed write to an offline disk
Onnn Represents one or more ASM slave processes that form a pool of connections to the ASM instance
for exchanging messages
PZ9n Represents one or more parallel slave processes that are used for fetching data on clustered ASM
installations from GV$ views

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ASM Instance Designs:
Case 1: Non-clustered ASM and Oracle Databases
ASM disk group A ASM disk group B
Single-instance
database server
ASM instance
Oracle DB A
instance
Oracle DB B
instance
Oracle DB C
instance

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ASM Instance Designs:
Case 2: Clustered ASM for Clustered Databases
ASM instance 3
Oracle DB A
instance 1
Oracle DB A
instance 2
Oracle DB B
instance 1
ASM instance 2
ASM instance 1 ASM instance 4
Oracle DB B
instance 2
ASM disk group A ASM disk group B

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Oracle DB A
instance 1
Oracle DB B
instance 1
Oracle DB B
instance 2
ASM instance 2
ASM instance 1 ASM instance 3
Oracle DB C
instance 1
ASM disk group A ASM disk group B
ASM Instance Designs:
Case 3: Clustered ASM for Mixed Databases

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ASM Components: ASM Disk Group
The ASM disk group is the fundamental object that ASM manages. It:
• Consists of one or more ASM disks that provide space
• Includes self-contained metadata and logging information for management of space
within each disk group
• Is the basis for storage of ASM files
• Supports three disk group redundancy levels:
– Normal defaults to internal two-way mirroring of ASM files.
– High defaults to internal three-way mirroring of ASM files.
– External uses no ASM mirroring and relies on external disk hardware or redundant
array of inexpensive disks (RAID) to provide redundancy.
• Supports ASM files from multiple databases

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ASM Components: Failure Groups
A failure group is a subset of the disks in a disk group, which could fail at the same time
because of shared hardware.
• Failure groups enable mirroring of metadata and user data.
• Default failure group creation puts every disk in its own failure group.
• Multiple disks can be placed in a singe failure group.
• Failure groups apply only to normal and high redundancy disk groups.
– A normal redundancy disk group requires at least two failure groups to implement
two-way mirroring of files.
– A high redundancy disk group requires at least three failure groups to implement
three-way mirroring of files.
• A quorum failure group contains copies of voting files when they are stored in normal or
high redundancy disk groups.

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ASM Components: ASM Disks
ASM disks are the storage devices that are provisioned to ASM disk groups.
• Are formed from five sources as follows:
– A disk or partition from a storage array
– An entire physical disk or partitions of a physical disk
– Logical volumes (LV) or logical units (LUN)
– Network-Attached Files (NFS)
– Exadata grid disk
• Are named when they are added to a disk group by using a different name than the
operating system device name
• May use different operating system device names on different nodes in a cluster for the
same ASM disk
• Are divided into allocation units (AU) with sizes 1, 2, 4, 8, 16, 32, or 64 MB allowed

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ASM Components: ASM Files
ASM files are a limited set of file types stored in an ASM disk group.
Some supported file types:
• Are stored as a set or collection of data extents
• Are striped across all disks in a disk group
• Use names that begin with a plus sign (+), which are automatically generated or from
user-defined aliases
Control files Flashback logs Data Pump dump sets
Data files DB SPFILE Data Guard configuration
Temporary data files RMAN backup sets Change tracking bitmaps
Online redo and archive logs RMAN data file copies Disaster recovery configurations
ASM and DB password files Transport data files ASM SPFILE

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ASM Files: Extents and Striping
ASM can use variable size data extents to support larger files, reduce memory
requirements, and improve performance.
• Each data extent resides on an individual disk.
• Data extents consist of one or more allocation units.
• For disk groups with AU size less than 4MB:
– Equal to AU for the first 20,000 extents (0–19999)
– Equal to 4 × AU for the next 20,000 extents (20000–39999)
– Equal to 16 × AU for extents above 40,000
ASM stripes files by using extents with a coarse method for load balancing or a fine method
to reduce latency.
• Coarse-grained striping is always equal to the effective AU size.
• Fine-grained striping is always equal to 128 KB.

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ASM Files: ASM File Mirroring
ASM mirroring is specified at the file level.
• Two files can share the same disk group with one file being mirrored while the other
is not.
• ASM allocates extents for a file with the primary and mirrored copies in different
failure groups.
• The mirroring options for ASM disk group types are:
Disk Group Type Supported
Mirroring Levels
Default
Mirroring Level
External redundancy Unprotected (None) Unprotected (None)
Normal redundancy Two-way
Three-way
Unprotected (None)
Two-way
High redundancy Three-way Three-way

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ASM Clients
Any active database instance that is using ASM storage and is currently connected to the
ASM instance is an ASM client.
• Connected ASM clients can be viewed:
– By using the asmcmd lsct disk_group command
– In the v$asm_client dynamic performance view
• Each file in ASM is associated with a single database.
Oracle DB A
instance
Oracle DB B
instance
Oracle DB C
instance
ASM instance
ADVM Mounted ACFS
OCR

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ASM Utilities
Many utilities can be used for ASM administration. These utilities may include:
• Oracle Universal Installer (OUI)
• ASM Configuration Assistant (ASMCA)
• Oracle Enterprise Manager (EM)
• SQL*Plus
• ASM Command-Line utility (ASMCMD)
• Server controller utility (srvctl)

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Q
Select the utilities that can be used to configure or manage ASM.
a. ASM Configuration Assistant (ASMCA)
b. Oracle Enterprise Manager (EM)
c. Database Configuration Assistant (DBCA)
d. SQL*Plus
e. ASM Command-Line utility (ASMCMD)
Quiz

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Summary
In this lesson, you should have learned how to describe the following:
• Automatic Storage Management (ASM) architecture
• Components of ASM