When a new disk group is created, a set of ASM file templates copied from the default
templates in Table 4-5 is saved with the disk group; as a result, individual template characteristics
can be changed and apply only to the disk group where they reside. In other words, the DATAFILE
system template in disk group +DATA1 may have the default coarse striping, but the DATAFILE
template in disk group +DATA2 may have fine striping. You can create your own templates in
each disk group as needed.
When an ASM datafile is created with the DATAFILE template, by default the datafile is
100MB and autoextensible, and the maximum size is 32767MB (32GB).
Chapter 4: Physical Database Layouts and Storage Management 107
Administering ASM Disk Groups
Using ASM disk groups benefits you in a number of ways: I/O performance is improved, availability
is increased, and the ease with which you can add a disk to a disk group or add an entirely new
disk group enables you to manage many more databases in the same amount of time. Understanding
the components of a disk group as well as correctly configuring a disk group are important goals
for a successful DBA.
In this section, I??™ll delve more deeply into the details of the structure of a disk group. Also, I??™ll
review the different types of administrative tasks related to disk groups and show how disks are
assigned to failure groups, how disk groups are mirrored, and how disk groups are created,
dropped, and altered.
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