ORACLE 10GR2 如何修改ASM AU_SIZE的大小

在ORACLE 11GR2 ASM 版本在用 ASMCA工具创建diskgroup 时可以指定AU_SIZE的大小，但在10GR2 ASM版本中AU_SIZE默认定义1m，不能修改，
而在实际生产环境中数据量有可能达到上TB或PB的数据量， 如果都是1M的EXTENT的话，那将严重的影响到数据库读写和访问性能，以下方面介绍如何修改
10gR2 AU_SIZE的大小
_asm_ausize的默认值是1M，_asm_stripesize默认值是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.