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.
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:
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 InstancesThe 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:
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:
StartUp/Shutdown Commands on an ASM InstanceWhen 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:
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