现象：在Oracle 12.2.0.1 RAC环境，在其ASM实例中，如果添加不同大小或者不同数量的LUN到failgroup中，会报错：
ORA-15032: not all alterations performed
ORA-15410: Disks in disk group OCRVT do not have equal size.
或者
ORA-15032: not all alterations performed
ORA-15411: Failure groups in disk group OCRVT have different number of disks.
解决方案：
动态修改这两个隐藏参数可以解决：
alter system set "_asm_disable_failgroup_size_checking"=true;
alter system set "_asm_disable_dangerous_failgroup_checking"=true;
下面举一个实际的例子：
比如新加的LUN：mpathi，mpathj，mpathk都是200M大小，以前的ASM磁盘组OCRVT由3个LUN：mpatha，mpathb，mpathc都是1G大小组成；现在想把新的LUN加到OCRVT磁盘组中：
SQL> select name, failgroup, path, mode_status, voting_file from v$asm_disk;
NAME FAILGROUP PATH MODE_ST V
----------------------------------- ------------------------------ --------------------------------------------- ------- -
/dev/mapper/mpathj ONLINE N
/dev/mapper/mpathi ONLINE N
/public/nfsdisk ONLINE N
/dev/mapper/mpathk ONLINE N
DATA_0001 DATA_0001 /dev/mapper/mpathf ONLINE N
FRA_0000 FRA_0000 /dev/mapper/mpathh ONLINE N
DATA_0002 DATA_0002 /dev/mapper/mpathg ONLINE N
DATA_0000 DATA_0000 /dev/mapper/mpathe ONLINE N
MGMT_0000 MGMT_0000 /dev/mapper/mpathd ONLINE N
OCRVT_0000 OCRVT_0000 /dev/mapper/mpathc ONLINE Y
OCRVT_0002 OCRVT_0002 /dev/mapper/mpathb ONLINE Y
OCRVT_0001 OCRVT_0001 /dev/mapper/mpatha ONLINE Y
12 rows selected.
直接尝试添加新的LUN到ASM磁盘组OCRVT中，会报错。依次尝试设置相关的隐藏参数，可以成功添加：
SQL> alter diskgroup ocrvt add FAILGROUP OCRVT_0000 disk '/dev/mapper/mpathi';
alter diskgroup ocrvt add FAILGROUP OCRVT_0000 disk '/dev/mapper/mpathi'
*
ERROR at line 1:
ORA-15032: not all alterations performed
ORA-15410: Disks in disk group OCRVT do not have equal size.
SQL> alter system set "_asm_disable_dangerous_failgroup_checking"=true;
System altered.
SQL> alter diskgroup ocrvt add FAILGROUP OCRVT_0000 disk '/dev/mapper/mpathi';
alter diskgroup ocrvt add FAILGROUP OCRVT_0000 disk '/dev/mapper/mpathi'
*
ERROR at line 1:
ORA-15032: not all alterations performed
ORA-15411: Failure groups in disk group OCRVT have different number of disks.
SQL> alter system set "_asm_disable_failgroup_size_checking"=true;
System altered.
SQL> alter diskgroup ocrvt add FAILGROUP OCRVT_0000 disk '/dev/mapper/mpathi';
Diskgroup altered.
总结：
asm中与failgroup相关的隐藏参数:
_asm_disable_dangerous_failgroup_checkingFALSE
_asm_disable_failgroup_count_checkingFALSE
_asm_disable_failgroup_size_checkingFALSE
SQL> r
1 SELECT i.ksppinm name,
2 i.ksppdesc description,
3 CV.ksppstvl VALUE
4 FROM sys.x$ksppi i, sys.x$ksppcv CV
5 WHERE i.inst_id = USERENV ('Instance')
6 AND CV.inst_id = USERENV ('Instance')
7 AND i.indx = CV.indx
8 AND i.ksppinm LIKE '%¶m%'
9* ORDER BY REPLACE (i.ksppinm, '_', '')
Enter value for param: failgroup
old 8: AND i.ksppinm LIKE '%¶m%'
new 8: AND i.ksppinm LIKE '%failgroup%'
NAME DESCRIPTION VALUE
----------------------------------- ------------------------------------------------------------------ ------------------------------
_asm_disable_dangerous_failgroup_ch Disable checking for dubious failgroup configurations FALSE
ecking
_asm_disable_failgroup_count_checki Disable checking for failure group count FALSE
ng
_asm_disable_failgroup_size_checkin Disable checking for failure group size FALSE
g
--这类参数实测可以动态修改：
alter system set "_asm_disable_failgroup_size_checking"=true;
alter system set "_asm_disable_dangerous_failgroup_checking"=true;
--alter system set "_asm_disable_failgroup_count_checking"=true; 这个参数我没有测出来实际作用，实测只需要上面两个参数设置为true就同样可以允许failgroup的数量不一致。
SQL> show parameter _asm
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
_asm_disable_dangerous_failgroup_che boolean TRUE
cking
_asm_disable_failgroup_size_checking boolean TRUE
--test
SQL> select name, failgroup, path, mode_status, voting_file from v$asm_disk;
NAME FAILGROUP PATH MODE_ST V
----------------------------------- ------------------------------ --------------------------------------------- ------- -
/public/nfsdisk ONLINE N
OCRVT_0005 OCRVT_0002 /dev/mapper/mpathk ONLINE N
OCRVT_0004 OCRVT_0001 /dev/mapper/mpathj ONLINE N
DATA_0001 DATA_0001 /dev/mapper/mpathf ONLINE N
OCRVT_0003 OCRVT_0000 /dev/mapper/mpathi ONLINE N
FRA_0000 FRA_0000 /dev/mapper/mpathh ONLINE N
DATA_0002 DATA_0002 /dev/mapper/mpathg ONLINE N
DATA_0000 DATA_0000 /dev/mapper/mpathe ONLINE N
MGMT_0000 MGMT_0000 /dev/mapper/mpathd ONLINE N
OCRVT_0000 OCRVT_0000 /dev/mapper/mpathc ONLINE Y
OCRVT_0002 OCRVT_0002 /dev/mapper/mpathb ONLINE Y
OCRVT_0001 OCRVT_0001 /dev/mapper/mpatha ONLINE Y
12 rows selected.
--以下操作均可以成功:
alter diskgroup ocrvt drop disk OCRVT_0003;
alter diskgroup ocrvt add FAILGROUP OCRVT_0000 disk '/dev/mapper/mpathi';
--如果不改参数，那么只能同时删除/增加每个failgroup中的成员:
alter diskgroup ocrvt drop disk OCRVT_0003, OCRVT_0004, OCRVT_0005;
alter diskgroup ocrvt add FAILGROUP OCRVT_0000 disk '/dev/mapper/mpathi'
FAILGROUP OCRVT_0001 disk '/dev/mapper/mpathj'
FAILGROUP OCRVT_0002 disk '/dev/mapper/mpathk';
--最后同样可以动态还原配置：
alter system set "_asm_disable_failgroup_size_checking"=false;
alter system set "_asm_disable_dangerous_failgroup_checking"=false;
注意：实验发现如果使用asmca添加磁盘，无论是否设置这个参数，都会报错[DBT-30003] The size of the disks selected is not the same as to allow for an equal number of 4MB AU size blocks.
而使用命令行操作，只要设置这2个隐藏参数为true即可成功。