Datasheet

20 Chapter 1
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Using Oracle ASM
You can reference the disk group and the disk name by joining the V$ASM_DISK and
V$ASM_DISKGROUP views, as shown in this query:
select adg.name dg_name, ad.name fg_name, path
from v$asm_disk ad
right outer join v$ASM_DISKGROUP adg
on ad.group_number=adg.group_number
where adg.name=’DGROUP1’;
DG_NAME FG_NAME PATH
-------- --------------- ----------------------------------------
DGROUP1 DGROUP1_0000 /oracle01/oradata/asm/disk group1.dsk
Why Tiered Storage?
Tiered database storage attempts to reduce the overall costs of disk storage in databases.
When you configure ASM, you might want to consider configuring different disk groups
for different kinds of tiered storage.
For example, suppose you work at Amalgamated General Consolidated. You have a new
database that you are designing. You can choose from fast and expensive solid-state disks
that costs $50 a gigabyte. Then there are the Fibre Channel disks that are a bit slower but
only $30 a gigabyte. Finally, there are the slow SATA drives at $20 a gigabyte.
You can, of course, architect your 1 terabyte database with all solid-state disks at a cost of
$50 million. It will be fast, no doubt, but is this the best choice for Amalgamated?
Amalgamated decides to analyze the needs of the database and determine if it can benefit
from a tiered storage approach. If you determined that you need only 100GB of solid-state
disk and that you could store the remaining 900GB on your $20 SATA drives, that would be
cost savings of $27 million. That’s quite a big savings.
This type of architecture requires that you architect physical database objects to sit
across these layers using partitioning, creating the more heavily used partitions on
better-performing disk; the infrequently used partitions can be moved over time to the
cheaper/slower disks. This might take more time and effort, but in the end the dollar
savings can be significant! Tiered storage is an idea that is very much taking off!
Dropping an ASM Disk Group
To remove an ASM disk group, you use the drop diskgroup command. By default, if any
files exist in the disk group, ASM will not allow you to drop it unless you use the
including
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