Hidden Initialization Parameters - Secrets of the Oracle Database - page 34

ASM Instance Setup
Next, we will create some cooked files for ASM storage. ASM will use these files instead of raw
disks. On Windows, the undocumented switch -create of the asmtool command is used to
create cooked files for use by ASM. The syntax is as follows:
asmtool -create <file_name> <file_size_mb>
We will use the asmtool command to create four files which will serve as “disks”. Each file
has a size of 512 MB.
C:\> mkdir C:\oradata
C:\> asmtool -create C:\oradata\ARRAY1_DISK1 512
Repeat the asmtool command with the file names ARRAY1_DISK2 , ARRAY2_DISK1 , and
ARRAY2_DISK2 to create three more files. On UNIX, the dd command is available to accomplish
the same task as asmtool -create . Following is an example for creating a file with a size of 512 MB:
$ dd if=/dev/zero bs=1048576 count=512 of=ARRAY1_DISK1
The above dd command reads 512 blocks with a size of 1 MB each from the device special
file /dev/zero . Since reading from /dev/zero returns nothing but binary zeros, the resulting file
is zeroed out as required by ASM. The dd command is available for Windows systems by installing
Cygwin ( http://www.cygwin.com ). Th e dd option conv=notrunc is interesting in that it may be
used to zero out a section within a file to simulate a failure or induce a block corruption.
The four files will be used to simulate two disk arrays (ARRAY1 and ARRAY2) with two
logical units (LUNs) each. We will then set up ASM to mirror across the two arrays. Striping
occurs within the array boundaries.
C:\oradata>ls -l
total 2463840
-rw-rw-rw- 1 ndebes mkpasswd 536870912 Nov 2 13:34 ARRAY1_DISK1
-rw-rw-rw- 1 ndebes mkpasswd 536870912 Nov 2 13:38 ARRAY1_DISK2
-rw-rw-rw- 1 ndebes mkpasswd 536870912 Nov 2 13:40 ARRAY2_DISK1
-rw-rw-rw- 1 ndebes mkpasswd 536870912 Nov 2 13:38 ARRAY2_DISK2
To start an ASM instance, a parameter file that contains INSTANCE_TYPE=ASM is required.
The parameter ASM_DISKSTRING is used to indicate where ASM should search for disks. Create a
file called pfile+ASM.ora with the following contents in %ORACLE_HOME%\database :
instance_type = ASM
asm_diskstring = 'c:\oradata\*'
Next, create a Windows service for the ORACLE ASM instance with oradim :
C:> oradim -new -asmsid +ASM -syspwd secret -startmode manual -srvcstart demand
Instance created.
The command oradim creates and starts a Windows service called OracleASMService+ASM.
You may verify that the service is running with net start .
C:> net start | grep -i asm
OracleASMService+ASM
Now we are ready to start the ASM instance.