Datasheet

10 Chapter 1
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Using Oracle ASM
The MARK process is responsible for marking ASM allocation units as stale following
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a missed write to an offline disk.
The RBAL process runs in both database and ASM instances. RBAL is responsible for
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performing a global open of ASM disks in normal databases. RBAL coordinates rebal-
ance activity for disk groups in ASM instances.
ASM Disk Discovery
ASM disk discovery is the first step to setting up an ASM disk group. In this section, we
will cover configuring the
ASM_DISKSTRING parameter, which helps with ASM disk discov-
ery, and then we will discuss the topic of ASM disk discovery in general.
Setting the ASM_DISKSTRING Parameter
When you configured the parameter file for your ASM instance, you configured a parameter
called
ASM_DISKSTRING. This parameter contains the paths that Oracle will use to try to find
the various candidate disks available for ASM’s use. The process of ASM finding disks in the
ASM_DISKSTRING path is known as discovery.
You may not need to set
ASM_DISKSTRING. ASM_DISKSTRING has a number of different
default values depending on the platform you are using. Table 1.1 lists the platform-
specific default values (these will be set if
ASM_DISKSTRING is set to a NULL value only).
TABLE 1.1 Default ASM Disk String
Platform Name Default ASM_DISKSTRING Value
AIX
/dev/rhdisk*
HP-UX /dev/rdsk/*
Linux /dev/raw/*
Mac OS X /dev/rdisk*s*s1
Solaris /dev/rdsk/*
Tru64UNIX /dev/rdisk/*
You can have multiple locations in the ASM_DISKSTRING parameter (we will provide an
example of this in just a moment). If you insert a ? placeholder at the beginning of the string,
Oracle will expand that out to represent the location of
ORACLE_HOME in the parameter values.
The
ASM_DISKSTRING can be dynamically altered, which is nice if your friendly system admin-
istrator adds some storage to your system that you want Oracle to be able to use. If you hap-
pen to change
ASM_DISKSTRING dynamically and the new disk path is not present, it will revert
to the old disk path. Removing an existing disk path, when that disk path is in use, will result
in a failure of the command.
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