Procedure: Adding a New ASM Disk to an Existing Diskgroup

Environment Scope:

• Oracle RAC environments
  
• Standalone servers with Oracle ASM-managed storage
  
• Linux servers using ASMLib or udev for disk management
  

Prerequisites:

• Approved maintenance window
  
• Storage team has provisioned new LUNs
  
• LUNs visible on all RAC nodes
  
• udev/ASMLib configured
  
• GRID/ASM privileges
  

ASM Disk Header Status Reference:

Status	Description
CANDIDATE	New disk ready to use
PROVISIONED	Disk provisioned via ASMLib
MEMBER	Disk already part of a diskgroup
FORMER	Previously used disk; currently not part of any diskgroup

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Step 1: Verify New Disk Visibility

1. Login to all RAC nodes and confirm the LUNs are visible at the OS level:
   

# Example for Node1

ls -ltr /dev/oracleasm/disks/

2. Check udev/ASMLib rules:
   

cat /etc/udev/rules.d/99-asm.rules | grep ASM_ORADATA_022

3. Verify disk permissions and ownership:
   

ls -l /dev/oracleasm/disks/ASM_ORADATA_022

# Output should show: brw-rw—- 1 oracle dba …

4. Check ASM disk header status in SQL:
   

col name for a20

col header_status for a15

col path for a45

SELECT GROUP_NUMBER, name, header_status, path, state, mode_status, total_mb, free_mb 

FROM v$asm_disk 

WHERE path=’/dev/oracleasm/disks/ASM_ORADATA_022′;

Expected Header Status: CANDIDATE

At this point, disk is ready to be added.

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Step 2: Test Disk Health Using a Dummy Diskgroup

Purpose: Ensure the disk is healthy before adding to production diskgroup.

1. Create a temporary ASM diskgroup:
   

CREATE DISKGROUP TESTDISK EXTERNAL REDUNDANCY DISK ‘/dev/oracleasm/disks/ASM_ORADATA_022’;

2. Verify diskgroup status and usage:
   

SELECT GROUP_NUMBER, NAME, TYPE, STATE, TOTAL_MB/1024 “TOTAL GB”, FREE_MB/1024 “FREE GB”, 

       ROUND(((TOTAL_MB – FREE_MB)/TOTAL_MB)*100,2) “%Used”, ROUND((FREE_MB/TOTAL_MB)*100,2) “%Free”

FROM v$asm_diskgroup 

WHERE NAME=’TESTDISK’;

3. Test tablespace creation:
   

CREATE TABLESPACE TEST_TS DATAFILE ‘TESTDISK’ SIZE 2G;

DROP TABLESPACE TEST_TS;

4. Drop the dummy diskgroup:
   

DROP DISKGROUP TESTDISK;

5. Verify disk header status:
   

SELECT name, header_status FROM v$asm_disk WHERE path=’/dev/oracleasm/disks/ASM_ORADATA_022′;

# Status should now show FORMER

Disk has passed health check and is ready for production.

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Step 3: Add Disk to Actual Diskgroup

1. Add disk and start rebalance:
   

ALTER DISKGROUP ORADATA02 ADD DISK ‘/dev/oracleasm/disks/ASM_ORADATA_022’ REBALANCE POWER 7;

2. Monitor rebalance operation:
   

SELECT * FROM v$asm_operation;

⚠️ The rebalance may take time depending on disk size and ASM workload.

3. Verify disk addition:
   

SELECT GROUP_NUMBER, NAME, HEADER_STATUS, PATH, STATE, MODE_STATUS, TOTAL_MB, FREE_MB 

FROM v$asm_disk 

WHERE path=’/dev/oracleasm/disks/ASM_ORADATA_022′;

# Status should show MEMBER

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Step 4: Post-Addition Validation

• Check ASM diskgroup free space and usage:
  

SELECT NAME, TOTAL_MB/1024 “TOTAL GB”, FREE_MB/1024 “FREE GB”

FROM v$asm_diskgroup

WHERE NAME=’ORADATA02′;

• Check rebalance completion:
  

SELECT * FROM v$asm_operation;

• Confirm all nodes see the new disk using asmcmd or V$ASM_DISK.
  

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Notes & Best Practices

• Always verify disk health with a dummy diskgroup before adding to production.
  
• Use REBALANCE POWER to control impact on running database workloads.
  
• Ensure udev/ASMLib rules are consistent across all nodes.
  
• Track disk header status changes in V$ASM_DISK:
  

Status Change	Meaning
CANDIDATE → FORMER	Disk tested in dummy diskgroup
FORMER → MEMBER	Disk added to production diskgroup