Creating new Oracle 18c ASM Disk Groups

Creating New Volumes

Create the new ASM volume(s) using your storage platform, for this blog I have created 3 volumes on a Pure FlashArray, simply providing names and sizes.

Create new ASM Volume(s)

Note the Volume serial numbers,  these will be used in the multipath configuration wwid (World Wide Identifier)

New ASM volumes

SCSI storage device serial numbers are universally unique. Each one starts with a 36bit (9 hexadecimal digit) vendor ID. Because the vendor ID is always the same for Pure Storage FlashArray volumes (3624a9370), it is omitted from the CLI and GUI displays.

Linux Configuration

Create multipath entries in  ‘/etc/multipath.conf’ for the 3 new volumes, in the examples below the wwid (World Wide Identifier) is set to Vendor ID + Serial number. e.g. ‘3624a9370’ + ‘ff551cc46aee54bf9000126ab’.
Note, the ‘wwid’ needs to be in lowercase and the ‘alias’ name for ASM disks needs to be less than 30 characters, alphanumeric and only use the ‘_ ‘ special character. 


Update multipath Configuration

Flush unused multipath devices

# multipath -F

Reload multipath configuration:

# service multipathd reload

Load and display multipath configuration, device mapper and other components

# multipath -v2
# multipath -ll

Oracle ASM Disk Discovery

Before we update our UDEV rules, lets check our Oracle ASM discovery disk string ‘ASM_DISKSTRING’.

Using asmcmd

ASMCMD> dsget
parameter:/u01/shared_config/ocr_configuration,  /dev/pureasm
profile:/u01/shared_config/ocr_configuration, /dev/pureasm

Using sqlplus

SQL> show parameter ASM_DISKSTRING;

asm_diskstring string /u01/shared_config/ocr_configuration, /dev/pureasm

We can now edit or create a UDEV rules file to reflect the ASM discovery string destination, the SYMLINK prefixes .


Reload UDEV rules as the root user using ‘udevadm trigger’ to set ownership and create links to the ASM disk discovery directory.

ls -la /dev/pureasm

We can now ready to create the ASM Disk Groups using the SQLPlus or the Oracle ASM Configuration Assistant ‘asmca’ UI.

I repeated this 3 times, creating +DATA. +FRA and +CONTROL_REDO which I will use in my next Blog Post, where I plan to share how to migrate from a file systems to Oracle ASM.


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