I??™ll also briefly review the EM Database Control interface to ASM; at the
command line, I??™ll also give you an introduction to the asmcmd command-line utility that you
can use to browse, copy, and manage ASM objects.
Disk Group Architecture
As defined earlier in this chapter, a disk group is a collection of physical disks managed as a unit.
Every ASM disk, as part of a disk group, has an ASM disk name that is either assigned by the DBA
or automatically assigned when it is assigned to the disk group.
Files in a disk group are striped on the disks using either coarse striping or fine striping. Coarse
striping spreads files in units of 1MB each across all disks. Coarse striping is appropriate for a
system with a high degree of concurrent small I/O requests, such as an OLTP environment.
Alternatively, fine striping spreads files in units of 128KB, is appropriate for traditional data
warehouse environments or OLTP systems with low concurrency, and maximizes response
time for individual I/O requests.
System Template External
Redundancy
Normal Redundancy High Redundancy Striping
CONTROLFILE Unprotected Two-way mirroring Three-way mirroring Fine
DATAFILE Unprotected Two-way mirroring Three-way mirroring Coarse
ONLINELOG Unprotected Two-way mirroring Three-way mirroring Fine
ARCHIVELOG Unprotected Two-way mirroring Three-way mirroring Coarse
TEMPFILE Unprotected Two-way mirroring Three-way mirroring Coarse
BACKUPSET Unprotected Two-way mirroring Three-way mirroring Coarse
XTRANSPORT Unprotected Two-way mirroring Three-way mirroring Coarse
PARAMETERFILE Unprotected Two-way mirroring Three-way mirroring Coarse
DATAGUARDCONFIG Unprotected Two-way mirroring Three-way mirroring Coarse
FLASHBACK Unprotected Two-way mirroring Three-way mirroring Fine
CHANGETRACKING Unprotected Two-way mirroring Three-way mirroring Coarse
AUTOBACKUP Unprotected Two-way mirroring Three-way mirroring Coarse
DUMPSET Unprotected Two-way mirroring Three-way mirroring Coarse
TABLE 4-5 ASM File Template Defaults
108 Oracle Database 11g DBA Handbook
Disk Group Mirroring and Failure Groups
Before defining the type of mirroring within a disk group, you must group disks into failure groups.
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