Datasheet

4 Chapter 1
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Using Oracle ASM
Using ASM in the Real World
If you are an Oracle database administrator, ASM will very much be on your mind if you
have to deal with Oracle database clustering (RAC). Early on in the architecting process,
you will have to decide how to store shared files because RAC depends on sharing of
database datafiles among the different nodes of the cluster.
You have several options, including shared raw devices and vendor-supplied products.
Another option is ASM sitting on top of Oracle Clusterware. This combination can often
provide a less-expensive solution over the vendor-supplied options and is easier to man-
age than raw disk storage. ASM and Clusterware are very popular options, and it is likely
you will encounter them in your Oracle career.
One very positive thing, from a business point of view, is that ASM is included as part of
your Oracle database license. This makes Oracle Clusterware/ASM an attractive alternative
to products from other vendors that charge extra for their clustering solutions.
At one location we are familiar with, the move to ASM was cautious but direct. Oracle
Clusterware was installed and ASM was sitting on top. All new Oracle RAC installs
started using ASM instead of shared raw disk partitions. The flash recovery area (FRA)
was also moved to ASM. Older RAC databases were moved to ASM over time, and now
all clustered databases are using ASM.
We also note that Oracle’s future direction calls for the elimination of raw devices for
storage of database datafiles. This will make movement to an ASM solution even more
attractive.
Creating the ASM Instance
In the following sections, we will review how to create an ASM instance. First we will
cover creating the ASM instance with the Oracle Database Configuration Assistant. Then
we will cover how to manually create an ASM instance.
Creating the ASM Instance with the DBCA
The DBCA is a Java-based tool that you can use to create or remove Oracle databases. For-
tunately for us, it can also be used to create or remove ASM instances. You can create the
ASM instance at any time, regardless of whether a database already exists. In Exercise 1.1,
you will see how to create an ASM instance.
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