After the storage administrator provides you with the disk for the database and presents the disk to the server, you want to stamp the disks as ASMLIB disks using the oracleasm command. All options to the oracleasm script that are not read-only actions require root privileges to execute. Such options include commands to configure, create, delete, and rename.

Example 1: Check oracleasm status

Before we can start using orale ASM, the oracleasm module must be loaded and psuedo filesystem /dev/oracleasm must be mounted. The oracleasm enable command simply writes to the configuration file to autostart ASMLIB. You can disable ASMLIB as part of the reboot process by using the oracleasm disable command. To check the status of both use the below command:

# oracleasm status
Checking if ASM is loaded: yes
Checking if /dev/oracleasm is mounted: yes

Example 2: Scan ASM disks

When you have create new asmdisk on one of cluster node, you need to scan disks on other nodes. For example:

At Node 1

[[email protected] ~]# oracleasm createdisk DATA1 /dev/sdd1
Writing disk header: done
Instantiating disk: done
[[email protected] ~]#  oracleasm createdisk DATA2 /dev/sde1
Writing disk header: done
Instantiating disk: done
[[email protected] ~]# oracleasm listdisks
DATA1
DATA2

At Node 2

At first there will not be any disk discovered on the 2nd node of the RAC. For example:

[[email protected] ~]# oracleasm listdisks
(There are no ASM disks)

After scanning the disk, you shall see 2 new disks getting “Instantiating” on 2nd node as well.

[[email protected] ~]# oracleasm scandisks
Reloading disk partitions: done
Cleaning any stale ASM disks…
Scanning system for ASM disks…
Instantiating disk “DATA1”
Instantiating disk “DATA2”

Example 3: Determine if a disk belongs to Oracle ASMlib

You can read a disk header using “oracleasm querydisk” command and determine if the disk belongs to ASM or not. For example:

# oracleasm querydisk /dev/sde1
Device “/dev/sde1” is marked an ASM disk with the label “DATA2”     ### this belongs to ASMLIB
# oracleasm querydisk /dev/sdb1
Device “/dev/sdb1” is not marked as an ASM disk   ### this does’nt belong to ASMLIB

Example 4: Check ASM Disk Group device path name

To get the absolute device path for the disks used while creating an ASM disk, we can use the below command:

# oracleasm querydisk -p VOTEDISK1
Disk “VOTEDISK1″ is a valid ASM disk
/dev/sdc1: LABEL=”VOTEDISK1″ TYPE=”oracleasm”

As you can see /dev/sdc1 is the absolute device path for the ASM disk with label “VOTEDISK1”.

Example 5. Rename ASM Disk

Sometime you may want to rename a ASM disk label. “oracleasm renamedisk” does the job of renaming the ASM disk label as well as re-instatiating the disks on the same node where rename was performed. It also removed the old ASM disk label while doing so. For example:

# oracleasm renamedisk -f VOTEDISK1 OCRVOTEDISK1
Instantiating disk “OCRVOTEDISK1”: done
Writing disk header: done
Removing old ASM disk “VOTEDISK1”: done

# oracleasm renamedisk -f VOTEDISK2 OCRVOTEDISK2
Instantiating disk “OCRVOTEDISK2”: done
Writing disk header: done
Removing old ASM disk “VOTEDISK2”: done

# oracleasm renamedisk -f VOTEDISK3 OCRVOTEDISK3
Instantiating disk “OCRVOTEDISK3”: done
Writing disk header: done
Removing old ASM disk “VOTEDISK3”: done

# oracleasm renamedisk -f DATADISK1 DBDATADISK1
Instantiating disk “DBDATADISK1”: done
Writing disk header: done
Removing old ASM disk “DATADISK1”: done
# oracleasm listdisks
DBDATADISK1
OCRVOTEDISK1
OCRVOTEDISK2
OCRVOTEDISK3

Example 5: Re-instantiating ASM Disks at another of RAC nodes after renaming disks

When you rename the disk on one node of the RAC, you will have to rescan the devices again on the other nodes of the RAC. This will re-instatiate the ASM disks and cleanup the old ASM disk labels. For example:

# oracleasm scandisks
Reloading disk partitions: done
Cleaning any stale ASM disks…
Cleaning disk “DATADISK1”
Cleaning disk “VOTEDISK1”
Cleaning disk “VOTEDISK2”
Cleaning disk “VOTEDISK3”
Scanning system for ASM disks…
Instantiating disk “DBDATADISK1”
Instantiating disk “OCRVOTEDISK1”
Instantiating disk “OCRVOTEDISK2”
Instantiating disk “OCRVOTEDISK3”

Example 6: Delete/Unmark ASM labels

Theoracleasm deletedisk command deletes the disk label that identifies the disk as the ASMLIB disk.

# oracleasm deletedisk DBDATADISK1
Removing ASM disk "DBDATADISK1":                      [  OK  ]
CentOS / RHEL : Installing and Configuring ASMLib