ORA-15031: Disk Specification Matches No Disks - ASM Discovery

ORA-15031: Disk Specification ‘path’ Matches No Disks

Error Overview

Error Text: ORA-15031: disk specification '/path/to/disk' matches no disks

ORA-15031 occurs during CREATE DISKGROUP, ALTER DISKGROUP ADD DISK, or ALTER DISKGROUP RESIZE when the path or pattern provided doesn’t match any disk visible to the ASM instance. ASM scans paths defined by asm_diskstring plus any explicit paths in the command and reports which ones produced no candidates.

Common Causes

Discovery String Mismatch

• Path not included in asm_diskstring parameter
• Wildcard pattern doesn’t match actual device names
• ASMLib path used but ASMLib not configured
• Spaces or escaping issues in shell-passed paths

Permissions Issues

• Grid OS user (typically grid) cannot read device
• UDEV rules not applied or stale
• Device owned by oracle instead of grid/asmadmin
• SELinux blocking access

Device Not Yet Discovered

• New LUN presented but oracleasm scandisks not run
• Multipath not yet aware of new device
• Server has not rescanned SCSI bus
• ASMLib createdisk not executed

Wrong Path Format

• Passing /dev/sdb when ASM expects /dev/oracleasm/disks/DISK1
• Including partition number when whole disk required (or vice versa)
• Using filesystem path instead of raw device

Diagnostic Steps

Verify Discovery String

-- Connect as SYSASM
sqlplus / as sysasm

SHOW PARAMETER asm_diskstring;

-- Check what ASM currently sees
SELECT path, header_status, mount_status, label
FROM v$asm_disk
ORDER BY path;

Test Path Manually

-- Force discovery of specific path
SELECT path, header_status FROM v$asm_disk
WHERE path = '/dev/oracleasm/disks/DISK5';

-- Add path to discovery and retry
ALTER SYSTEM SET asm_diskstring='/dev/oracleasm/disks/*,/dev/mapper/mpath*' SCOPE=MEMORY;

SELECT path FROM v$asm_disk WHERE path LIKE '%DISK5%';

Check OS-Level Visibility

# Verify device exists
ls -la /dev/oracleasm/disks/DISK5
ls -la /dev/mapper/mpathf

# Check permissions (grid user must own)
# Should show: grid asmadmin
stat /dev/oracleasm/disks/DISK5

# Test readability as grid user
sudo -u grid cat /dev/oracleasm/disks/DISK5 | head -c 100 > /dev/null
echo "Exit: $?"

# Verify ASMLib state
oracleasm status
oracleasm listdisks
oracleasm querydisk -p DISK5

Inspect ASM Discovery Patterns

# Check candidate disks at OS level
ls -la /dev/oracleasm/disks/
ls -la /dev/mapper/

# Verify multipath
multipath -ll | grep -i "size"

Resolution Steps

1. Update asm_diskstring

Add the missing path pattern to asm_diskstring:

-- View current value
SHOW PARAMETER asm_diskstring;

-- Update to include new path
ALTER SYSTEM SET asm_diskstring='/dev/oracleasm/disks/*,/dev/mapper/mpath*'
  SCOPE=BOTH;

-- Verify ASM sees the disk now
SELECT path, header_status FROM v$asm_disk WHERE path LIKE '%DISK5%';

2. Fix Permissions

# Set correct ownership for ASM access
chown grid:asmadmin /dev/sdb1
chmod 660 /dev/sdb1

# For ASMLib disks
oracleasm createdisk DISK5 /dev/sdb1
oracleasm scandisks
oracleasm listdisks

# Apply UDEV rules
cat > /etc/udev/rules.d/99-oracle-asmdevices.rules <<EOF
KERNEL=="sdb1", OWNER="grid", GROUP="asmadmin", MODE="0660"
EOF

udevadm control --reload-rules
udevadm trigger

3. Discover New LUN

# Rescan SCSI bus for new LUNs
for h in /sys/class/scsi_host/host*; do
    echo "- - -" > $h/scan
done

# Update multipath
multipath -v3
multipath -ll

# Update ASMLib
oracleasm scandisks
oracleasm listdisks

# Verify in ASM
sqlplus / as sysasm
SQL> SELECT path FROM v$asm_disk WHERE header_status='CANDIDATE';

4. Use Correct Path Format

-- For ASMLib environments
ALTER DISKGROUP data ADD DISK '/dev/oracleasm/disks/DISK5';

-- For multipath without ASMLib
ALTER DISKGROUP data ADD DISK '/dev/mapper/mpathf';

-- For raw partitions
ALTER DISKGROUP data ADD DISK '/dev/sdb1';

-- For ASM Filter Driver (AFD)
ALTER DISKGROUP data ADD DISK 'AFD:DISK5';

5. Cluster-Wide Consistency

In RAC, all nodes must see the disk:

# Verify on each node
for node in node1 node2; do
    ssh $node "ls -la /dev/oracleasm/disks/DISK5"
    ssh $node "stat /dev/oracleasm/disks/DISK5 | grep -i access"
done

# Force cluster-wide rescan
crsctl stat res -t | grep -i diskgroup

Common Scenarios

Scenario 1: Adding Disk After New LUN Provision

ALTER DISKGROUP data ADD DISK '/dev/oracleasm/disks/DISK5';
ORA-15031: disk specification '/dev/oracleasm/disks/DISK5' matches no disks

Fix: Run oracleasm scandisks on all nodes, then retry.

Scenario 2: New ASM Diskstring

CREATE DISKGROUP fra EXTERNAL REDUNDANCY DISK '/dev/mapper/mpathx';
ORA-15031: disk specification '/dev/mapper/mpathx' matches no disks

Fix: Add /dev/mapper/mpath* to asm_diskstring.

Scenario 3: Permission Mismatch

Disk visible at OS but ASM cannot match it.

Fix: Check disk is readable by grid user via sudo -u grid dd if=/dev/sdb1 of=/dev/null bs=1M count=1.

Sample Output

SQL> ALTER DISKGROUP data ADD DISK '/dev/oracleasm/disks/DISK5';
ALTER DISKGROUP data ADD DISK '/dev/oracleasm/disks/DISK5'
*
ERROR at line 1:
ORA-15032: not all alterations performed
ORA-15031: disk specification '/dev/oracleasm/disks/DISK5' matches no disks

SQL> SHOW PARAMETER asm_diskstring;
NAME              TYPE        VALUE
----------------- ----------- ------------------
asm_diskstring    string      /dev/mapper/mpath*

-- asm_diskstring doesn't include /dev/oracleasm/disks/*

Prevention Strategies

Maintain Comprehensive Discovery String

-- Cover all expected path schemes
ALTER SYSTEM SET asm_diskstring=
  '/dev/oracleasm/disks/*,/dev/mapper/mpath*,AFD:*'
  SCOPE=BOTH;

Pre-Provision Validation Script

#!/bin/bash
# Validate disk before adding to ASM
DISK=$1

if [ ! -e "$DISK" ]; then
    echo "ERROR: $DISK does not exist"
    exit 1
fi

OWNER=$(stat -c '%U:%G' "$DISK")
if [ "$OWNER" != "grid:asmadmin" ]; then
    echo "ERROR: $DISK owned by $OWNER, expected grid:asmadmin"
    exit 1
fi

if ! sudo -u grid dd if="$DISK" of=/dev/null bs=1M count=1 2>/dev/null; then
    echo "ERROR: grid user cannot read $DISK"
    exit 1
fi

echo "OK: $DISK ready for ASM"

Cluster-Wide Verification

#!/bin/bash
NODES="node1 node2"
DISK="/dev/oracleasm/disks/DISK5"

for node in $NODES; do
    echo "=== $node ==="
    ssh $node "ls -la $DISK 2>&1; stat -c 'owner=%U group=%G mode=%a' $DISK 2>&1"
done

Related Errors

• ORA-15014: Path is not in the discovery set
• ORA-15020: Discovered duplicate ASM disk
• ORA-15025: Could not open disk
• ORA-15032: Not all alterations performed
• ORA-15042: ASM disk is missing

Troubleshooting Checklist

• Verify asm_diskstring includes path pattern
• Confirm device exists and is readable by grid user
• Run oracleasm scandisks for ASMLib
• Run multipath -v3 for multipath devices
• Verify cluster-wide visibility in RAC
• Check UDEV rules for permission persistence
• Use correct path format for environment