ORACLE ASM DISKGROUP MODIFICATION OR ALTERATION

1)  
      Controller 1:
/devices/diska1
/devices/diska2
/devices/diska3
/devices/diska4
       Controller 2:
/devices/diskb1
/devices/diskb2
/devices/diskb3
/devices/diskb4
The SQL statement in Example 4–1 creates a disk group named data with normal redundancy consisting of two failure groups controller1
 or controller2 with four disks in each failure group. The data disk group is typically used to store database data files.
Example 4–1 Creating the DATA disk group

CREATE DISKGROUP data NORMAL REDUNDANCY
FAILGROUP controller1 DISK
'/devices/diska1' NAME diska1,
'/devices/diska2' NAME diska2,
'/devices/diska3' NAME diska3,
'/devices/diska4' NAME diska4
FAILGROUP controller2 DISK
'/devices/diskb1' NAME diskb1,
'/devices/diskb2' NAME diskb2,
'/devices/diskb3' NAME diskb3,
'/devices/diskb4' NAME diskb4
ATTRIBUTE 'au_size'='4M',
'compatible.asm' = '11.2',
'compatible.rdbms' = '11.2',



2)Example 4–5 Managing volumes with ALTER DISKGROUP VOLUME statements

SQL> ALTER DISKGROUP data ADD VOLUME volume1 SIZE 10G;
Diskgroup altered.

SQL> ALTER DISKGROUP data RESIZE VOLUME volume1 SIZE 15G;
Diskgroup altered.

SQL> ALTER DISKGROUP data DISABLE VOLUME volume1;
Diskgroup altered.

SQL> ALTER DISKGROUP data ENABLE VOLUME volume1;
Diskgroup altered.

SQL> ALTER DISKGROUP ALL DISABLE VOLUME ALL;
Diskgroup altered.

SQL> ALTER DISKGROUP data DROP VOLUME volume1;
Diskgroup altered.

3)If /devices/diskc3 was previously a member of a disk group
that no longer exists, then you could use the FORCE option
to add the disk as a member of another disk group.
For example, the following use of the FORCE clause
enables /devices/diskc3 to be added to data2,
even though it is a current member of data3.
For this statement to succeed, data3 cannot be mounted.

ALTER DISKGROUP data2 ADD DISK
'/devices/diskc3' FORCE;



4)A DROP FORCE operation leaves data at reduced redundancy until
the subsequent rebalance operation completes. This increases
your exposure to data loss if there is a subsequent disk failure
during rebalancing. Use DROP FORCE with caution.



5)Resizing disks in disk groups

ALTER DISKGROUP data1
RESIZE DISKS IN FAILGROUP failgrp1 SIZE 100G;


6)you to cancel all pending drops of disks within disk groups.
If a drop disk operation has completed, then this statement
cannot be used to restore it.

ALTER DISKGROUP data1 UNDROP DISKS;


7)SQL> SELECT name, header_status, path FROM V$ASM_DISK
WHERE path LIKE '/devices/disk0%'
NAME HEADER_STATUS PATH
--------- ------------- ---------------------
FORMER /devices/disk02
FORMER /devices/disk01
CANDIDATE /devices/disk07
DISK06 MEMBER /devices/disk06
DISK05 MEMBER /devices/disk05
DISK04 MEMBER /devices/disk04
DISK03 MEMBER /devices/disk03

-->disks that have a disk group name in the disk header, show a header status of MEMBER.
-->Disks that were discovered, but that have not yet been assigned to a disk group, have a status of either CANDIDATE or PROVISIONED.
-->Disks that previously belonged to a disk group and were dropped cleanly from the disk group have a status of FORMER.
-->When adding a disk, the FORCE option must be used if Oracle ASM recognizes that the disk was managed by Oracle.
Such a disk appears in the V$ASM_DISK view with a status of FOREIGN.


8)SQL> SELECT name, type, total_mb, free_mb, required_mirror_free_mb,
usable_file_mb FROM V$ASM_DISKGROUP;
NAME  TYPE    TOTAL_MB  FREE_MB    REQUIRED_MIRROR_FREE_MB              USABLE_FILE_MB
----- ------- ------   ----------  -----------------------               --------------
DATA  NORMAL    6144       3768           1024                                 1372

(FREE_MB - REQUIRED_MIRROR_FREE_MB) / 2 = USABLE_FILE_MB
(3768 - 1024) / 2 = 2744 / 2 = 1372


9)The following example takes disk DATA_001 offline and drops it after five minutes.

ALTER DISKGROUP data OFFLINE DISK DATA_001 DROP AFTER 5m;

This example brings all of the disks in disk group DATA online:
ALTER DISKGROUP data ONLINE ALL;

SQL>SELECT GROUP_NUMBER, OPERATION, STATE FROM V$ASM_OPERATION;
GROUP_NUMBER OPERA STAT
------------ ----- ----
1            ONLIN RUN


10)
Checking the Internal Consistency of Disk Group Metadata
1.By default, the CHECK DISK GROUP clause verifies all of the metadata directories
2.ASM displays summary errors and writes the details about the errors in an alert log
3.Cross checks all of the file extent maps and allocation tables for consistency
4.Verifies that the alias directory tree is linked correctly
5.Checks that Oracle ASM metadata directories do not have unreachable allocated blocks
6.The REPAIR | NOREPAIR clause specifies whether Oracle ASM should attempt to repair errors that are found during the check. The default is NOREPAIR.

ALTER DISKGROUP data1 CHECK ALL;