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Non-violence
is the greatest force at
the disposal of mankind. It is mightier than the mightiest
weapon of destruction devised by the ingenuity of man.
Gandhi |
Automatic Storage
Management (ASM) in the Oracle 10g database
Introduction
ASM provides a vertical
integration of the file system and the volume manager that is
specifically built for Oracle database files. Its key features and
benefits are:
· Stripes files
rather than logical volumes
· Online disk
reconfiguration and dynamic rebalancing
· Adjustable
rebalancing speed
· Provides
redundancy on a file basis
· Supports only
Oracle database files
· Custer-aware
· Automatically
installed
ASM instance do not have a
data dictionary and it is restricted to few SQL commands and Dynamic
Performance view. The following are some example of SQL commands.
Commands:
SQL> STARTUP/SHUTDOWN
SQL> ALTER DISKGROUP
MOUNT/DISMOUNT
SQL> ALTER DISKGROUP
ONLINE/OFFLINE DISK
SQL> ALTER DISKGROUP
REBALANCE
SQL> ALTER DISKGROUP
CHECK
Views:
V$ASM_TEMPLATE
V$ASM_DISKGROUP
V$ASM_CLIENT
V$ASM_FILE
V$ASM_ALIAS
V$ASM_DISK
V$ASM_OPERATION
Hands-On #1-Creating and
deleting disk groups
The following are examples
of creating and deleting disk groups.
Creating a disk-group:
SQL> CREATE DISKGROUP
dgora1 NORMAL REDUNDANCY
FAILGROUP controller1 DISK
/dev/rdsk/c0t0d0s2
NAME mydisk SIZE 200G FORCE,
/dev/rdsk/c0t1d0s2,
/dev/rdsk/c0t2d0s2
FAILGROUP controller2 DISK
/dev/rdsk/c1t0d0s2,
/dev/rdsk/c1t1d0s2,
/dev/rdsk/c1t2d0s2;
Dropping a diskgroup:
SQL> DROP DISKGROUP
dgora1 INCLUDING CONTENTS;
Hands-On #2-Adding and
removing disks
The following are examples
of how to add disks to an existing disk group.
SQL> ALTER DISKGROUP
dgora1
ADD FAILGROUP controller1
/dev/rdsk/c0t3d0s2
NAME a5;
To remove a disk:
SQL> ALTER DISKGROUP
dgora1 DROP DISK a5;
To undo the removed disk do
the following SQL statement. This only works if the status of drop is
pending or the drop function was not completed yet.
SQL> ALTER DISKGROUP
dgora1 UNDROP DISKS;
Hands-On # 3-Starting ASM
and Displaying diskgroups
Assuming you started your
ASM instance.
$ ORACLE_SID=+ASM; export
ORACLE_SID
$ sqlplus /nolog
SQL> CONNECT / AS SYSDBA
SQL> STARTUP
Display a list of your
diskgroups.
SQL> SELECT name FROM
v$asm_diskgroup;
Display a list of
associated ASM disks.
SQL> COL name FORMAT a20
SQL> COL failgroup
FORMAT a20
SQL> SELECT name,
failgroup, bytes_read, bytes_written
FROM v$asm_disk
/
Display a list of
associated ASM files.
SQL> SELECT group_number,
file_number, bytes, type, striped
FROM v$asm_file
/
Open another session with
different instance:
$ ORACLE_SID=school; export
ORACLE_SID
$ $ sqlplus /nolog
SQL> CONNECT / AS SYSDBA
Display a list of all your
datafiles.
SQL> COL file_name
FORMAT a40
SQL> SELECT file_name,
tablespace_name
FROM dba_data_files
/
Hands-On # 4-Using the ASM
diskgroup
Create a tablespace that is
stored in the ASM disk group dgora1.
SQL> CREATE TABLESPACE
mytablespace2
DATAFILE +dgora1 SIZE
100m
/
Display a list of all your
datafiles. What do see?
SQL> COL file_name
FORMAT a40
SQL> SELECT file_name,
tablespace_name
FROM dba_data_files
/
Now, you should have one
more line.
Go back on your ASM
instance and display a list of associated ASM files.
SQL> SELECT group_number,
file_number, bytes, type, striped
FROM v$asm_file
/
The result should be
different from before. You added one more datafile to it.
Add one addition disk to
your system.
SQL> HOST dd
if=/dev/zero of=/u02/oradata/school/diska abs=1024k count=200
SQL> SELECT name,
failgroup, bytes_read, bytes_written
FROM v$asm_disk
/
SQL> ALTER DISKGROUP
dgora1
ADD DISK /u02/oradata/school/diska
/
Execute the following query
until you get no rows selected.
SQL> SELECT operation,
est_minutes
FROM v$asm_operation
/
Again, display a list of
associated ASM disks.
SQL> SELECT name,
failgroup, bytes_read, bytes_written
FROM v$asm_disk
/
Now, you should see one
more disk was added to disk group.
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We must learn to
live together as brothers or perish together as fools. Martin
Luther King Jr. |
Questions:
Questions on
Automatic
Storage Management (ASM) in the Oracle 10g database
Q: What does ASM provide?
Q: What are its key
features and benefits?
Q: Does ASM have a data
dictionary?
Q: How do you create a disk
group by using ASM?
Q: How do you delete a disk
group by using ASM?
Q: How do you add a disk to
an existing disk group?
Q: How do you remove a disk
to an existing disk group?
Q: Can you undo the removed
disk? How?
Q: How do you display a
list of your diskgroups?
Q: How do you display a
list of associated ASM disks?
Q: How do you display a
list of associated ASM files?
Q: How do you create a
tablespace that uses an ASM disk group?
Q: How do you add one
addition disk to your system?
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