Datasheet

Working with the ASM Instance

In this case, we have created a disk group called dgroup1. It is using normal redundancy

and the default template. Two named failure groups are assigned, diskcontrol1 and diskcon-

trol2. Each failure group represents one physical or logical disk unit, which has been dis-

covered by ASM. Two separate disks and failure groups are required because of the normal

redundancy. If we used high redundancy, we would need to add a third disk to the command,

as shown here:

CREATE DISKGROUP dgroup1 HIGH REDUNDANCY

failgroup diskcontrol1 DISK

‘/devices/diska1’ NAME diska1

failgroup diskcontrol2 DISK

‘/devices/diskb1’ NAME diskb1

failgroup diskcontrol3 DISK

‘/devices/diskc1’ NAME diskc1;

You might have noticed the name clause in the create diskgroup command example

earlier. You can also name the disks being assigned to the ASM disk group using the

name

clause of the

create diskgroup command. Failure to use the name clause will result in each

disk receiving its own system-default assigned name.

When you create an ASM disk group, Oracle will add that disk group to the

ASM_

DISKGROUPS

parameter on the ASM instance only if you are using an spﬁle. If you are

not using an spﬁle, you will need to manually add the disk group to the

ASM_DISKGROUPS

parameter. The

ASM_DISKGROUPS parameter tells Oracle which disk groups it should

mount when the ASM instance is started. You can see the

ASM_DISKGROUPS parameter

setting by using the

show parameter command from SQL*Plus, as shown here:

SQL> show parameter ASM_DISKGROUPS

NAME TYPE VALUE

------------------------------------ ----------- --------------------------

ASM_DISKGROUPS string COOKED_DGROUP1, SP_DGROUP2

If you do not add the disk group to the ASM_DISKGROUPS parameter, you will need to

manually mount the disk group.

You might have noticed that each time we create a new disk group (and when we add

new disks to a disk group), we give the disk a name. For example, here we create a new disk

group called

DGROUP1:

CREATE DISKGROUP dgroup1 EXTERNAL REDUNDANCY

failgroup diskcontrol1 DISK

‘/oracle01/oradata/asm/disk group1.dsk’ NAME dgroup1_0000;

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