Understanding ORA-01115

The ORA-01115 error indicates an I/O (input/output) error while Oracle attempted to read a block from a datafile. This is typically a hardware or storage-related error that signifies a serious underlying problem.

ORA-01115: IO error reading block from file %s (block # %s)

ORA-01110: data file %s: '%s'

ORA-27072: File I/O error (additional OS-specific error)

This error is often accompanied by OS-specific error messages that provide additional context about the nature of the I/O failure.

Common Causes

1. Disk Hardware Failure

Bad sectors, failing disk drives, or degraded RAID arrays can cause read failures on specific blocks.

2. Storage Area Network (SAN) Issues

Path failures, HBA problems, or SAN fabric issues can result in intermittent or persistent I/O errors.

3. Filesystem Corruption

Corrupted filesystem metadata or journaling issues can prevent successful reads of database files.

4. NFS/Network Storage Problems

Network timeouts, NFS server issues, or mount option problems when using networked storage.

5. Virtualization Issues

Storage thin provisioning running out of space, or hypervisor storage connectivity problems in virtual environments.

Diagnostic Steps

Step 1: Check OS-Level Errors

# Linux - Check system messages
dmesg | grep -i error
tail -100 /var/log/messages

# Check disk health
smartctl -a /dev/sda

# View I/O statistics
iostat -x 5

Step 2: Verify Datafile Accessibility

# Test file read
dd if=/u01/oradata/ORCL/users01.dbf of=/dev/null bs=8192

# Check file permissions
ls -la /u01/oradata/ORCL/

# Verify filesystem
df -h /u01/oradata/

Step 3: Oracle Block Verification

-- Use DBV to identify bad blocks
$ dbv file=/u01/oradata/ORCL/users01.dbf blocksize=8192

-- Check RMAN for corrupt blocks
RMAN> BACKUP VALIDATE DATAFILE 4;

Resolution Methods

Method 1: Block Media Recovery

If only specific blocks are affected and you have RMAN backups:

RMAN> BLOCKRECOVER DATAFILE 4 BLOCK 127;

-- Or recover multiple blocks
RMAN> BLOCKRECOVER 
      DATAFILE 4 BLOCK 127, 128, 129
      DATAFILE 5 BLOCK 45;

Method 2: Restore and Recover Datafile

-- Take datafile offline
SQL> ALTER DATABASE DATAFILE 4 OFFLINE;

-- Restore from backup
RMAN> RESTORE DATAFILE 4;
RMAN> RECOVER DATAFILE 4;

-- Bring back online
SQL> ALTER DATABASE DATAFILE 4 ONLINE;

Method 3: Relocate Datafile

Move the datafile to healthy storage:

SQL> ALTER DATABASE DATAFILE '/u01/oradata/users01.dbf' 
     OFFLINE;

-- Copy to new location (OS level)
$ cp /u01/oradata/users01.dbf /u02/oradata/users01.dbf

SQL> ALTER DATABASE RENAME FILE 
     '/u01/oradata/users01.dbf' TO '/u02/oradata/users01.dbf';

SQL> RECOVER DATAFILE '/u02/oradata/users01.dbf';
SQL> ALTER DATABASE DATAFILE '/u02/oradata/users01.dbf' ONLINE;
⚠️ Hardware Check Required

ORA-01115 errors often indicate failing hardware. Before attempting recovery, have your storage team verify the health of the underlying storage system.

Method 4: Using DBRECOVER

When I/O errors prevent standard recovery, DBRECOVER can read around bad blocks and extract data: 

DBRECOVER> open datafile '/u01/oradata/ORCL/users01.dbf'
[WARN] I/O error on blocks: 127-129, 456
[INFO] Skipping bad blocks, reading available data
[INFO] Found 234 tables

DBRECOVER> recover table ORDERS skip_bad_blocks
[INFO] Processing 45,678 rows
[WARN] 12 rows in bad blocks - skipped
✓ Recovered 45,666 rows

Prevention Strategies

  1. Storage Monitoring: Implement proactive storage health monitoring
  2. RAID Configuration: Use appropriate RAID levels with hot spares
  3. Regular Backups: Ensure frequent, validated backups
  4. ASM Usage: Consider Oracle ASM for automatic storage management
  5. Redundant Paths: Implement multipathing for SAN storage
  6. UPS Protection: Protect against power-related corruption

Need Expert Help?

For persistent ORA-01115 errors or when hardware issues complicate recovery, contact us at [email protected]