12c以前的更换磁盘步骤见：http://blog.itpub.net/22621861/viewspace-1320369/

12c开始，更换ASM磁盘更加便捷。

首先确认当前ASM磁盘和磁盘组的对应情况。

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$ sqlplus / as sysasm
col disk_name format a20
col diskgroup_name format a40
select a.name as disk_name, b.name as diskgroup_name from v$asm_disk a, v$asm_diskgroup b
where a.group_number = b.group_number;

DISK_NAME DISKGROUP_NAME
-------------------- ----------------------------------------
DATA1 DATA
DATA2 DATA
DATA3 DATA
FRA1 FRA
FRA2 FRA
FRA3 FRA
OCR1 OCRV
OCR2 OCRV
OCR3 OCRV
VD1 OCRV
VD2 OCRV
VD3 OCRV

计划更换磁盘OCR1，确认当前该ASM磁盘对应设备

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# oracleasm querydisk /dev/sdc1
Device "/dev/sdc1" is marked an ASM disk with the label "OCR1"

处于Online状态的磁盘不能replace，否则会发生报错：

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SQL> alter diskgroup OCRV replace disk OCR1 with '/dev/sdo1' power 4;
alter diskgroup OCRV replace disk OCR1 with '/dev/sdo1' power 4
*
ERROR at line 1:
ORA-15032: not all alterations performed
ORA-15145: ASM disk 'OCR1' is online and cannot be replaced.

尝试将OCR1磁盘offline，产生报错：

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SQL> ALTER DISKGROUP OCRV OFFLINE DISK OCR1;
ALTER DISKGROUP OCRV OFFLINE DISK OCR1
*
ERROR at line 1:
ORA-15032: not all alterations performed
ORA-15283: ASM operation requires compatible.rdbms of 11.1.0.0.0 or higher

根据MOS ID 1571975.1
需要设置参数。

先查看当前参数：

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SQL> select NAME ,COMPATIBILITY,DATABASE_COMPATIBILITY from v$asm_diskgroup where name='OCRV';
NAME
------------------------------------------------------------
COMPATIBILITY
--------------------------------------------------------------------------------
DATABASE_COMPATIBILITY
--------------------------------------------------------------------------------
OCRV
12.1.0.0.0
10.1.0.0.0

设置参数：

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SQL> ALTER DISKGROUP OCRV SET ATTRIBUTE 'COMPATIBLE.RDBMS'='12.1.0.0.0';
Diskgroup altered.
SQL> select NAME ,COMPATIBILITY,DATABASE_COMPATIBILITY from v$asm_diskgroup where name='OCRV';
NAME
------------------------------------------------------------
COMPATIBILITY
--------------------------------------------------------------------------------
DATABASE_COMPATIBILITY
--------------------------------------------------------------------------------
OCRV
12.1.0.0.0
12.1.0.0.0

此时，可以将磁盘offline

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SQL> ALTER DISKGROUP OCRV OFFLINE DISK OCR1;
Diskgroup altered.

要添加的磁盘需要符合以下条件：
1）RAC中其他节点也可访问；
2）设备所有者和权限符合要求，可用裸设备方式（详见http://blog.itpub.net/22621861/viewspace-2116865/）；
3）设备名符合参数asm_diskstring。

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SQL> alter system set asm_diskstring='ORCL:*','/dev/raw/raw*' sid='*' scope=both;
System altered.
SQL> show parameter asm_diskstring
NAME TYPE
------------------------------------ ----------------------
VALUE
------------------------------
asm_diskstring string
ORCL:*, /dev/raw/raw*

接下来，可以replace了

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alter diskgroup OCRV replace disk OCR1 with '/dev/raw/raw1' power 4;
Diskgroup altered.

确认

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col name format a10
col path format a20
select name,path,total_mb from v$asm_disk;
NAME PATH TOTAL_MB
---------- -------------------- ----------
OCR1 /dev/raw/raw1 4094

而此时，新磁盘也自动online了。

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select name,state from v$asm_disk;
NAME STATE
---------- ----------------
VD3 NORMAL
OCR1 NORMAL

此时ASM已经可以正常运行，asmlib却仍然将旧设备标记为ASM磁盘

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# oracleasm querydisk /dev/sdc1
Device "/dev/sdc1" is marked an ASM disk with the label "OCR1"

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//删除旧标记
# oracleasm deletedisk /dev/sdc1
Clearing disk header: done
Dropping disk: done
//其他节点运行
oracleasm scandisks

由于新更换的设备路径是裸设备，不是asmlib，所以不要在asmlib中创建。

至此，全部完成。

12c下更换ASM磁盘