Automatic Storage Management

Oracle ASM started with Oracle 10g provides volume and filesystem management where the I/O subsystem is directly handled

by the Oracle Kernel. It provides highly scalable and high availability storage instrastructure.

Each LUN is mapped as a disk. Disk are grouped together into disk group. ASM takes care of writiing / striping onto disk in the diskgroup.

i.e Database files are automatically spread over the available disks in the diskgroup it is done in extent level.

ASMCMD ASM Command line Utility.

Its an Explorer to the ASM disk system.

1) When you execute asmcmd we get to the root of the ASM system i.e '+'

2) On executing the ls -l, you get details of the diskgroup presents.

3) With normal commands like cd,ls,du,mkdir,rm you could manipulate the ASM filesystem

Helpful Commands

du (disk usage) : Shows us the total disk space occupied by ASM files in that directory (and its subdirectory)

lsct : Information about the current ASM clients

lsdg : Information about the diskgroup and their attributes

State : Current State of Diskgroup whether Mounted/Connected

Type : Diskgroup Redundancy (NORMAL,HIGH,EXTERNAL)

REBAL : Y if rebalance operation in progress

Unbal : Y is rebalancing is required by diskgroup

Sector : Sector size in bytes

Block : Block size in bytes

AU : Allocation Unit

Total_MB : Size of diskgroup in MB

Free_MB : Free Space in Diskgroup

Req_mir_free_MB : Space that is required in the diskgroup to restore full redundancy after worst failure that can be tolerated by diskgroup.


Offline_disks : Number of offline disks in the disk group.

Name : Disk group name.

rm : Removes files/directory which is equivalent to "ALTER DISKGROUP ..DROP FILE/DIRECTORY"