Configuration Options


This section reviews the various ways to set up and configure a database using ASM files, manage the ASM instance, and so on, which will be useful in the forthcoming section on ASM operations titled "Performing ASM Operations."

Automatic Storage Management is integrated into the database server. It is available in both the Enterprise Edition and Standard Edition installations. When you use Oracle Universal Installer, it will prompt you to install and configure a database using ASM or to install and configure an ASM instance without creating a database instance. When you create a database, Database Configuration Assistance (DBCA) searches for an existing ASM instance; if it does not find one, you have the option of creating and configuring one during the installation process. To configure the ASM instance using DBCA, choose the ASM disk(s) and create the disk group(s) on it by choosing available disk(s). (See the section titled "Performing ASM Operations" for more information on configuring disk groups.) The DBCA creates a separate instance called +ASM in the nomount stage, which controls your ASM installations. Choose all your data files, control files, redo logs, and SPFILEs for your ASM volumes. A typical ASM instance needs around 100MB of disk space.

ASM Installations on Linux

Those of you who are trying to install ASM on Linux systems should review the MetaLink Note #275315.1 and http://www.oracle.com/technology/tech/linux/asmlib/install.html to learn about the issues with setting up ASM files and about ASMLib. ASMLib is a support library for the ASM feature of Oracle Database 10g. This library will enable ASM I/O to Linux disks without standard UNIX I/O API limitations. This provides an alternative interface for the ASM-enabled kernel to identify and access block devices. It is not required to run ASM. The preceding documents describe the steps required to install the Linux-specific ASM library and its associated drivers on a Linux system. If you encounter issues with free space on disks, you can use MetaLink Note #266028.1 to use files instead of raw devices.


You cannot use the silent installation method for database installation (in UNIX) and create a database using ASM, because root.sh script has to be run before the database-creation step.

For the most part, an ASM instance is started and managed like any other database instance, except that the initialization parameter file contains the parameter INSTANCE_TYPE=ASM. Similarly, the ASM instance can be shut down like any other database instance using similar commands. For ASM instances, the mount option tries to mount only the disk groups that are specified by the ASM_DISKGROUPS initialization parameter and not the database. ASM instances require a much smaller SGA (typically 64MB). An ASM instance should be running at all times and should be brought up automatically on server reboots.

Refer to platform-specific release notes available on Oracle Technology Network (OTN) (http://www.oracle.com/technology/documentation/database10g.html) to get more details.


An ASM instance does not have a data dictionary, so you have to be SYSDBA or SYSOPER to connect to an ASM instance. Use the password file to connect remotely to an ASM instance. Those who connect with SYSDBA privilege will have complete administrative access to all disk groups in the system.

The SYSOPER privilege is limited to the following SQL commands: STARTUP and SHUTDOWN, ALTER DISKGROUP MOUNT/DISMOUNT/REPAIR, ALTER DISKGROUP ONLINE/OFFLINE DISK, ALTER DISKGROUP REBALANCE/CHECK, and access to all V$ASM_* views.

The storage measurement units vary in definition according to the user's context. Although many storage vendors and disk manufacturers consider 1,000 bytes to be 1KB, 1,000,000 bytes to be 1MB, and so on, Oracle considers 1,024 bytes to be 1KB and 1,048,576 bytes to be 1MB. So the actual values for these file sizes will vary depending on which calculations you use.


Automatic Storage Management has the following operational limits:

  • Maximum storage of 4 petabytes (4,000 terabytes) for each ASM disk and a maximum of 2.4 terabyte storage for each file

  • Maximum of 63 disk groups and a maximum of 1,000,000 files per disk group

  • Maximum of 10,000 ASM disks for a storage system

  • Storage of 40 exabytes (40x1,000,000 terabytes) per storage system

We will review the initialization parameters for an ASM instance in the next section, which will help you understand ASM operations.

Initialization Parameters for ASM Instances

The ASM instance has very few initialization parameters when compared with a database instance. The important parameters, along with their default values in parentheses, are given here:

  • INSTANCE_TYPE (ASM). This is the only required parameter. All other parameters have default values suited for most environments.

  • DB_UNIQUE_NAME (+ASM). This is the unique name for ASM (or group of instances) within the cluster or on the node.

  • ASM_DISKSTRING (NULL). This parameter limits the set of disks that ASM considers for recovery.

  • ASM_DISKGROUPS (NULL). This gives the list of names for disk groups mounted by the ASM instance at startup or when ALTER DISKGROUP ALL MOUNT is used. With SPFILE, you may rarely need to alter this dynamic value.

  • ASM_POWER_LIMIT (1). This parameter controls the maximum power on an ASM instance for disk rebalancing. Possible values range from 1 to 11, with 11 being the fastest and 1 the slowest. We discuss this parameter in detail later in this chapter in the section titled "RESIZE and REBALANCE Operations Operations."

  • LARGE_POOL_SIZE (8MB or higher). The large pool is used by ASM internal packages. For other buffer parameters, you can use the default values.

The initialization parameters that start with ASM can be used only for ASM instances. If you use any other database initialization parameter in an ASM initialization parameter file, it will cause one of the following scenarios:

  • For an invalid initialization parameter, the ASM instance will produce an ORA-15021 error.

  • For parameters related to buffer cache and dump destinations valid for ASM instance, those values will be accepted.

  • If you specify an ASM-specific parameter in a database instance, it will produce an ORA-15021 error.

StartUp/Shutdown Commands on an ASM Instance

When you connect to an ASM instance and issue the STARTUP command in SQL*Plus, it will try to mount the disk groups specified in ASM_DISKGROUPS instead of the database. Similarly, when you issue the command SHUTDOWN NORMAL, the ASM instance goes down like any other normal database. Other extensions to the STARTUP and SHUTDOWN commands on an ASM instance are interpreted as follows:

  • STARTUP MOUNT mounts the disk groups specified by ASM_DISKGROUPS.

  • STARTUP NOMOUNT does not mount any disk groups, but starts up the instance.

  • STARTUP OPEN is not valid for an ASM instance.

  • STARTUP FORCE issues the command SHUTDOWN ABORT to the ASM instance and restarts it.

  • SHUTDOWN NORMAL causes the ASM instance to wait for the connected ASM instances and other active ASM SQL sessions to exit before shutting down.

  • SHUTDOWN IMMEDIATE causes the ASM to wait for SQL sessions in progress to finish before shutting down. All database instances need not be disconnected to shut down the instance.

  • SHUTDOWN ABORT will immediately shut down the ASM instance.

  • SHUTDOWN TRANSACTIONAL is similar to the IMMEDIATE operation.



    Oracle Database 10g Insider Solutions
    SUSE LINUX Enterprise Server 9 Administrators Handbook
    ISBN: 672327910
    EAN: 2147483647
    Year: 2006
    Pages: 214

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