ORACLE 10GR2 ASM 如何修改AU_SIZE的大小

 在ORACLE 11GR2 ASM 版本在用 ASMCA工具建立diskgroup 時可以指定AU_SIZE的大小，但在10GR2 ASM版本中AU_SIZE預設定義1m，不能修改，
而在實際生產環境中資料量有可能達到上TB或PB的資料量， 如果都是1M的EXTENT的話，那將嚴重的影響到資料庫讀寫和訪問效能，以下方面介紹如何修改
10gR2 AU_SIZE的大小

_asm_ausize的預設值是1M，_asm_stripesize預設值是128K：
SQL> select name,value from sys.all_parameters where name like '_asm%';
 
NAME                                               VALUE
-----------------------------------   --------------------------------------------------------------------------------
_asm_disk_repair_time                              14400
_asm_ausize                                        1048576
_asm_blksize                                       4096
_asm_acd_chunks                                    1
_asm_libraries                                     ufs
_asm_maxio                                         1048576
_asm_allow_only_raw_disks                          TRUE
_asmlib_test                                       0
_asm_allow_resilver_corruption                     FALSE
_asmsid                                            asm
_asm_wait_time                                     18
_asm_stripewidth                                   8
_asm_stripesize                                    131072
_asm_droptimeout                                   60
_asm_emulmax                                       10000
_asm_emultimeout                                   0
_asm_kfdpevent                                     0
 
17 rows selected
   
Example:
The following example creates a diskgroup with 16MB Allocation Unit
(Data Extents) and allows for 1MB FINE striping for all data files:

1. Shut down the ASM instance

2. Edit the ASM init.ora parameter file and add:
   o _asm_ausize=16777216
   o _asm_stripesize=1048576

3. Restart the ASM instance

4. Create a disk group
   o CREATE DISKGROUP diskgroup_name disk '/devices/diska1','/devices/diska2';

5. Change all ASM file templates to FINE grained:
   o ALTER DISKGROUP diskgroup_name ALTER TEMPLATE ATTRIBUTES (FINE);
   o Repeat this command for all ASM file types. Attributes types are listed
     below:
   o CONTROLFILE, DATAFILE, ONLINELOG, ARCHIVELOG, TEMPFILE, BACKUPSET,
     PARAMETERFILE, DATAGUARDCONFIG, FLASHBACK, CHANGETRACKING, DUMPSET,
     XTRANSPORT, AUTOBACKUP

The 16MB AU setting with 1MB FINE grain striping continues to provide efficient
1MB striping of data as well as much lower ASM file extent overhead. This
configuration provides faster ASM file opens and supports 10TB to PB capacity
range ASM databases more effectively.