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The ASM_POWER_LIMIT parameter, the ASM_POWER_LIMIT parameter, controls the number of ARBx of the ASM background process. The ARBx process is used for ASM disk data redistribution and fragmentation. ASM_POWER_LIMIT values range from 0 to 11 (it is said that it can be set to 0 from 10gR2, 0 is not used to do reblance, and the default is 1. The higher the value, the faster the speed and the higher the performance requirements, especially when the host is busy). When a new disk is added or deleted, ASM will launch ARBx for IO dispersion operation, which is a very resource-consuming action, so be sure to do it when the system is idle. The default Stripe Size for stripe and allocation unit ASM of ASM is 128K. (the maximum IO of a general operating system is 1m, and for a system with a Block Size of 8K, generally speaking, the db_file_multiblock_read_count is set to 16.) The allocation unit (Allocation Unit) is 1m, and this AU corresponds to extent. In some DW environments, as the amount of data increases, the AU will be very large, which will have a performance impact. Stripe Size and AU can be adjusted by two implicit parameters on the ASM instance: _ asm_ausize_asm_stripesize (note that the maximum is 1m, otherwise it will have a negative impact)

The INSTANCE_TYPE:ASM instance requires this parameter to be ASM, implying that DB_UNIQUE_NAME is set to + ASM.ASM_DISKSTRING: specify the location that should be looked up during disk discovery, and the default value is NULL. ASM_DISKGROUPS: specifies the name of the disk group to be mounted automatically when the instance starts. The default value is NULL.

When ASM allocates space, it is carried out in the unit of AU, and AU is Allocation units, which is the basic unit of ASM disk.

In Oracle 10gR2, the default unit size of ASM AU is 1m, and the corresponding stripe size is 128K. In ASM, you can adjust by resizing the implied parameters of _ asm_ausize, and _ asm_stripesize controls the corresponding striped parameters.

You can query the relevant information from the v$asm_diskgroup view:

SQL > select group_number,name,sector_size,block_size,allocation_unit_size from v$asm_diskgroup

GROUP_NUMBER NAME SECTOR_SIZE BLOCK_SIZE ALLOCATION_UNIT_SIZE- 1 ARCHDG 512 4096 1048576 2 DATADG 512 4096 1048576 in Oracle Database 11g You can specify au_size:SQL > CREATE DISKGROUP DATA DISK'/ dev/raw/raw15','/ dev/raw/raw16','/dev/raw/raw17' ATTRIBUTE 'au_size' =' 16M', 'compatible.asm' =' 11.1' 'compatible.rdbms' =' 11.1' when creating a disk group with a statement similar to the following The relevant parameters allowed by ASM can be obtained from the instance of DB. The following are a series of initialization parameters related to asm: SQL > SELECT x.ksppinm NAME, y.ksppstvl VALUE, x.ksppdesc describ FROM SYS.x$ksppi x, SYS.x$ksppcv y WHERE x.indx = y.indx AND x.ksppinm LIKE'% asm%'

NAME VALUE DESCRIB-- asm_diskstring disk set Locations for discovery_asm_disk_repair_time 14400 seconds to wait before dropping a failing diskasm_diskgroups diskgroups to mount automaticallyasm_power_limit 1 number of processes for disk rebalancing_asm_ausize 1048576 allocation unit size_asm_blksize 4096 metadata block size_asm_acd_chunks 1 initial ACD chunks created_asm_libraries ufs library search order for discovery_asm_maxio 1048576 Maximum size of individual I/O request_asm_allow_only_raw_disks TRUE Discovery only raw devices_asmlib_test 0 Osmlib test event_asm_allow_resilver_corruption FALSE Enable disk resilvering for external redundancy_asmsid asm ASM instance id_asm_wait_time 18 Max/imum time to wait before asmb exits_asm_stripewidth 8 ASM file stripewidth _ asm_stripesize 131072 ASM file stripesize _ asm_droptimeout 60 timeout before offlined disks get dropped (in 3s ticks) _ asm_emulmax 10000 max number of concurrent disks to emulate errors_asm_emultimeout O errors_asm_emultimeout 0 timeout before emulation begins (in 3s ticks) _ asm_kfdpevent 0 KFDP event

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