Databases Reference
In-Depth Information
Setup disk groups
ASM organizes storage in Disk Groups, a concept similar to logical volumes, so
you have to ask the DBCA to define a new disk group, then click on the
Create
New
Button, this will display the
Create
Disk
Group
Window (
G
), where you can
define the disk group name (
H
) and the raw disk devices (
I
) that will be part of this
disk group; the DBCA will display all available candidate devices. If the expected
raw devices don't appear you can click on the
Change
Disk
Discovery
Path
(
J
)
button to look for raw devices on another path. If the raw devices don't appear after
changing the path, then validate the raw devices at the OS level and make sure the
OS properly recognizes the physical devices. Most DBA's configure at least two disk
groups, one for tablespaces and a second one for the flash recovery area, but you can
configure as many disk groups as you require.
Candidate devices are automatically discovered by the DBCA. If the DBCA is not
successful in finding candidate devices it could be because the device is already
in use, or the discovery path is not properly set, or it is not started by the OS. You
should refer to the specific OS documentation on how to setup and start raw devices.
In the particular case of Linux, you must make sure that the raw device has been
started using the Linux startup scripts, otherwise it won't be visible. The following
script was used to set up raw devices in Linux. This is included here only for
demonstration purposes, and it is not meant to be used in a production environment.
It creates files that will later be 'seen' as raw devices; a feature available in Linux
environments. Please take a look at the
losetup
,
raw
and
chown
commands. These
are the commands used to define and reactivate
raw
devices in Linux.
echo Preparing ASM disks ...
WHOAMI='whoami'
if [ $WHOAMI != root ] ; then
echo $0 must be run as root
exit 1
fi
if [ ! -d /u01/asmdisks ] ; then
mkdir -p /u01/asmdisks
fi
cd /u01/asmdisks
VDISK=0
DD=/bin/dd
LOSETUP=/sbin/losetup
RAW=/usr/bin/raw
LOGFILE=/tmp/asmsetup.log
date > $LOGFILE
while [ $VDISK -lt 5 ] ; do
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