本文主要介绍Oracle 11.2.0.3环境下ASM实例的管理，主要包含以下内容：
1：ASM磁盘及磁盘组的状态查看
2：创建external 冗余磁盘组,添加，删除磁盘
3：创建normal redundancy磁盘组
4：normal redundancy下的failgroup测试
5：删除ASM磁盘组
6：其他asm实例初始化参数含义

一：查看ASM磁盘及磁盘组状态
SQL> select * from v$asm_disk;
SQL> select * from v$asm_diskgroup;

二：创建external 冗余磁盘组,添加，删除磁盘，删除磁盘的时候需要指定磁盘的name而不是path

   SQL> create diskgroup FRA external redundancy disk '/dev/asm-disk4';   
    Diskgroup created.   
      
    SQL> alter diskgroup fra add disk '/dev/asm-disk5' rebalance power 10;   
    Diskgroup altered.   
      
    SQL> select name,failgroup,path from v$asm_disk;   
      
    NAME                 FAILGROUP            PATH   
    -------------------- -------------------- --------------------   
    DATA_0000            DATA_0000            /dev/asm-disk1   
    DATA_0001            DATA_0001            /dev/asm-disk3   
    DATA_0002            DATA_0002            /dev/asm-disk2   
    FRA_0000             FRA_0000             /dev/asm-disk4   
    FRA_0001             FRA_0001             /dev/asm-disk5   
                                              /dev/asm-disk6   
                                              /dev/asm-disk7   
      
    SQL> alter diskgroup fra drop disk '/dev/asm-disk4' rebalance power 10;   
    alter diskgroup fra drop disk '/dev/asm-disk4' rebalance power 10   
    *   
    ERROR at line 1:   
    ORA-15032: not all alterations performed   
    ORA-15054: disk "/DEV/ASM-DISK4" does not exist in diskgroup "FRA"   
      
    SQL> alter diskgroup fra drop disk 'FRA_0000' rebalance power 10;   
    Diskgroup altered.  

三：创建normal redundancy磁盘组

    SQL> conn /as sysasm   
    Connected.   
    SQL> create diskgroup fra normal redundancy    
         failgroup fg1 disk '/dev/asm-disk4','/dev/asm-disk5'   
         failgroup fg2 disk '/dev/asm-disk6','/dev/asm-disk7'   
         attribute 'compatible.rdbms'='11.2','compatible.asm'='11.2';   
    Diskgroup created.   
      
    SQL> select name, total_mb,free_mb,required_mirror_free_mb,usable_file_mb from v$asm_diskgroup;   
      
    NAME         TOTAL_MB    FREE_MB REQUIRED_MIRROR_FREE_MB USABLE_FILE_MB   
    ---------- ---------- ---------- ----------------------- --------------   
    DATA            61440      54873                       0          18291   
    FRA             81920      81592                   20480          30556  

四：failgroup测试；FAILGROUP是用于将磁盘分组，以保证丢失任何一组FAILGROUP磁盘，数据还是完整的,多用于多阵列，通过ASM来完成冗余的环境！
1：查看FRA磁盘组中failgroup信息及磁盘状态

    SQL> select name,path,failgroup,mount_status from v$asm_disk where group_number=2;   
      
    NAME                 PATH                 FAILGROUP  MOUNT_STATUS   
    -------------------- -------------------- ---------- ---------------------   
    FRA_0003             /dev/asm-disk7       FG2        CACHED   
    FRA_0002             /dev/asm-disk6       FG2        CACHED   
    FRA_0000             /dev/asm-disk4       FG1        CACHED   
    FRA_0001             /dev/asm-disk5       FG1        CACHED  

2：在rdbms实例中创建表空间，建表并插入数据，收集表统计信息

    SQL> create tablespace test01 datafile '+FRA';   
    Tablespace created.   
      
    ASMCMD> pwd   
    +fra/db/datafile   
    ASMCMD> ls   
    TEST01.256.800622493   
      
    SQL> create table t1 tablespace test01 as select * from dba_objects;   
    Table created.   
      
    SQL> exec dbms_stats.gather_table_stats('SYS','T1');   
    PL/SQL procedure successfully completed.   
      
    SQL> select count(*) from t1;   
      
      COUNT(*)   
    ----------   
         74501  

3：删除udev相关规则，重启数据库实例和ASM实例，验证数据是否存在

    SQL> conn /as sysasm   
    Connected.   
    SQL> alter diskgroup fra mount;   
    alter diskgroup fra mount   
    *   
    ERROR at line 1:   
    ORA-15032: not all alterations performed   
    ORA-15040: diskgroup is incomplete   
    ORA-15042: ASM disk "1" is missing from group number "2"   
    ORA-15042: ASM disk "0" is missing from group number "2"   
      
    SQL> alter diskgroup fra mount force;   
    Diskgroup altered.   
      
    SQL> select name,path,failgroup,mount_status from v$asm_disk;   
      
    NAME       PATH                 FAILGROUP            MOUNT_STATUS   
    ---------- -------------------- -------------------- ---------------------   
    FRA_0000                        FG1                  MISSING   
    FRA_0001                        FG1                  MISSING   
    FRA_0002   /dev/asm-disk6       FG2                  CACHED   
    FRA_0003   /dev/asm-disk7       FG2                  CACHED   
    DATA_0000  /dev/asm-disk1       DATA_0000            CACHED   
    DATA_0002  /dev/asm-disk2       DATA_0002            CACHED   
    DATA_0001  /dev/asm-disk3       DATA_0001            CACHED   
    7 rows selected.   
      
    SQL> conn /as sysdba   
    Connected.   
    SQL> select count(*) from t1;   
      
      COUNT(*)   
    ----------   
         74501  

五：删除ASM磁盘组，默认磁盘故障条件下，经过12960秒即3.6个小时后自动删除；删除磁盘组之前需要保证无数据存放在磁盘组上且无到该磁盘组的active连接

    [grid@localhost ~]$ tail -f /u01/app/grid/diag/asm/+asm/+ASM/trace/alert_+ASM.log    
    ORA-15062: ASM disk is globally closed   
    Thu Nov 29 12:00:53 2012   
    WARNING: Disk 0 (FRA_0000) in group 2 will be dropped in: (12960) secs on ASM inst 1   
    WARNING: Disk 1 (FRA_0001) in group 2 will be dropped in: (12960) secs on ASM inst 1   
    Thu Nov 29 12:00:58 2012   
      
    asm实例：   
    SQL> select path,name,repair_timer from v$asm_disk where group_number=2;   
      
    PATH                 NAME       REPAIR_TIMER   
    -------------------- ---------- ------------   
                         FRA_0000          12960   
                         FRA_0001          12960   
    /dev/asm-disk6       FRA_0002              0   
    /dev/asm-disk7       FRA_0003              0   
      
    SQL> alter diskgroup fra online disk 'FRA_0000';   
    Diskgroup altered.   
      
    SQL> alter diskgroup fra online disk 'FRA_0001';   
    Diskgroup altered.   
      
    SQL> select name,path,failgroup,mount_status from v$asm_disk;   
      
    NAME       PATH                 FAILGROUP            MOUNT_STATUS   
    ---------- -------------------- -------------------- ---------------------   
    FRA_0002   /dev/asm-disk6       FG2                  CACHED   
    FRA_0003   /dev/asm-disk7       FG2                  CACHED   
    DATA_0000  /dev/asm-disk1       DATA_0000            CACHED   
    DATA_0002  /dev/asm-disk2       DATA_0002            CACHED   
    DATA_0001  /dev/asm-disk3       DATA_0001            CACHED   
    FRA_0001   /dev/asm-disk5       FG1                  CACHED   
    FRA_0000   /dev/asm-disk4       FG1                  CACHED   
      
    SQL> drop diskgroup fra;   
    drop diskgroup fra   
    *   
    ERROR at line 1:   
    ORA-15039: diskgroup not dropped   
    ORA-15053: diskgroup "FRA" contains existing files   
      
    rdbms实例：   
    SQL> drop tablespace test01 including contents;   
    Tablespace dropped.   
      
    SQL> shutdown immediate   
    Database closed.   
    Database dismounted.   
    ORACLE instance shut down.   
      
    asm实例：   
    SQL> drop diskgroup fra including contents;   
    Diskgroup dropped.   
      
    rdbms实例：   
    SQL> startup   
    ORACLE instance started.   
      
    Total System Global Area  313860096 bytes   
    Fixed Size                  1344652 bytes   
    Variable Size             192940916 bytes   
    Database Buffers          113246208 bytes   
    Redo Buffers                6328320 bytes   
    Database mounted.   
    Database opened. 

六：其他asm实例初始化参数含义

instance_type：Defines the type of the instance, such as RDBMS and ASM. However, this has been made optional in an Oracle Grid Infrastructure ASM.

asm_power_limit：Manages the degree of parallelism to speed up the ASM disk rebalance operations, for example, whenever a disk is being dropped from an existing disk group or when the disk group rebalance is initiated manually. This is a dynamic parameter that can be set in the range from 0 to 11 (1024 in 11gR2 and above). Considering the size of a disk group, you may increase the limit of the  POWER to speed up the rebalancing operation. Multiple ASM instances can hold the different values across a cluster. When no limit is specified, it uses the default value for the rebalancing operation.

asm_diskstring: Used by the ASM instance to identify and discover the disks mentioned in the paths. Once the disks are discovered, they will appear in the V$ASM_DISK dynamic view. The disk discovery occurs when an ASM instance is initiated, when you issue a query against the  V$ASM_DISK/V$ASM_DISKGROUP dynamic views, or when you  MOUNT,  UNMOUNT,  RESIZE,  ADD  a disk. It is a dynamic parameter and you can specify multiple paths within this parameter

processes: Apart from the SGA initialization parameter value, the PROCESSES initialization parameter value has some influence over the ASM instance. Therefore, you may use the following formula to tune the  PROCESSES initialization parameter when multiple database instances are accessing the instance:
Processes = 50+50*n (where n indicates the number of instances used to connect to the ASM instance)