1.ASM disks
2.ASM diskgroups
3.ASM instance
4.ASM background processes
ASM disks : The disks which are labeled are used for ASM diskgroup creation are called ASM disks.
ASM disk is nothing but collection of allocation units. The size of allocation unit will be 1mb or 2mb or 4mb or 8mb or 16mb or 32mb or 64mb.
Every ASM file will have one or more allocation units. We can also specify the allocation unit size at the time of ASM diskgroup creation.
ASM diskgroup : This is something like a LUN that we create using third party volume manager.
ASM Instance : This is something like RDBMS instance but it has only diskgroups to mount but not database.
In the server we can have only one ASM instance(limitation).
ASM background processes : Apart from normal background processes, ASM instance has extra background processes like ASMB, ARBn,RBAL.
In the foreground ASM instance communicates with RDBMS instance with the help of ASMB background process.
Whenever we add a disk to the existing diskgroup, ARBn dynamically rebalances the data among all the disks in coordination with RBAL(rebalanace maaster).
Number of ARBn processes depends on the parameter "asm_power_limit".
