ORA-00205: Error in Identifying Control File - Recover Missing Control Files

ORA-00205: Error in Identifying Control File

Error Overview

Error Text: ORA-00205: error in identifying control file, check alert log for more info

The ORA-00205 error appears during database startup — specifically during the MOUNT phase — when Oracle cannot open or validate one or more of the control files specified in the CONTROL_FILES initialization parameter. The database will remain in NOMOUNT state and will not proceed to MOUNT or OPEN until all control files are accounted for and readable.

This is one of the most serious startup errors a DBA can face. The control file contains the physical structure of the database: datafile locations, redo log locations, checkpoint information, and backup history (if RMAN is used). Without a valid control file, the database cannot determine what data it owns or where it lives.

Common Causes

1. Control File Missing from the Expected Location

A control file was accidentally deleted, moved, or renamed at the OS level
A storage reconfiguration moved mount points without updating CONTROL_FILES
A disk failure destroyed the physical location where one or more control files resided

2. Control File Corrupted

Storage hardware error wrote bad sectors to the control file location
An unclean shutdown or system crash left the control file in a partially-written state
The file exists but Oracle’s internal checksum validation fails

3. CONTROL_FILES Parameter Points to Wrong Locations

The CONTROL_FILES parameter in the spfile or pfile was edited incorrectly
A DBA copied a pfile from another environment without updating file paths
A database was cloned or duplicated and the parameter was not updated for the new host

4. Storage or Mount Point Not Available at Startup

ASM diskgroup not mounted when the database startup is attempted
NFS mount not available at the time of startup
Symlinks pointing to control files resolve to non-existent targets

5. OS-Level Permissions Issue

The Oracle OS user does not have read/write permission on the control file path
SELinux or AppArmor policies blocking Oracle from accessing the file
Control file created by a different OS user during a restore operation

Diagnostic Queries

Check CONTROL_FILES Parameter

-- View the current control file locations (run from NOMOUNT state)
SHOW PARAMETER control_files;

-- Alternative query
SELECT name, value
FROM v$parameter
WHERE name = 'control_files';

-- If using an spfile, check what the spfile contains
SELECT name, value
FROM v$spparameter
WHERE name = 'control_files';

Verify Control File Status (from MOUNT state, if achievable)

-- Once mounted successfully, check control file details
SELECT
  name,
  status,
  is_recovery_dest_file,
  block_size,
  file_size_blks
FROM v$controlfile;

-- Check control file record sequence for consistency
SELECT
  cf_seq#               AS sequence_number,
  to_char(cf_timstamp, 'DD-MON-YYYY HH24:MI:SS') AS timestamp
FROM v$database;

-- Control file contents summary
SELECT type, record_size, records_total, records_used
FROM v$controlfile_record_section
ORDER BY type;

Review the Alert Log for Specific Error Details

-- The alert log will contain the exact error and file path
SELECT
  originating_timestamp,
  message_text
FROM v$diag_alert_ext
WHERE originating_timestamp > SYSDATE - 1
  AND (message_text LIKE '%ORA-00205%'
       OR message_text LIKE '%control file%'
       OR message_text LIKE '%ORA-00202%'
       OR message_text LIKE '%ORA-27037%')
ORDER BY originating_timestamp DESC
FETCH FIRST 20 ROWS ONLY;

-- Check the ADR home location for alert log file path
SELECT name, value FROM v$diag_info WHERE name IN ('ADR Home', 'Alert Log');

Check for Surviving Multiplexed Copies

-- After mounting with a surviving copy, verify all control files
-- Run after successful mount:
SELECT
  name,
  status
FROM v$controlfile
ORDER BY name;

-- Check if any control file is missing (status will be INVALID or file won't appear)

Step-by-Step Resolution

1. Read the Alert Log First

Before taking any recovery action, read the alert log to understand exactly which control file is missing and why:

# Find the alert log location from SQL*Plus (NOMOUNT state)
# SQL> SELECT value FROM v$diag_info WHERE name = 'Diag Trace';
# Then navigate to the alert log:

# Linux/Unix
tail -200 $ORACLE_BASE/diag/rdbms/<db_unique_name>/<instance_name>/trace/alert_<SID>.log

# Or use ADRCI
adrci
adrci> show alert -tail 100

The alert log will show lines like:

ORA-00202: control file: '/u01/oradata/orcl/control01.ctl'
ORA-27037: unable to obtain file status

This identifies exactly which file is missing.

2. Restore from a Multiplexed Copy (Fastest Recovery)

If the database has multiplexed control files (best practice) and at least one copy survives:

-- Step 1: Start in NOMOUNT to access parameters
STARTUP NOMOUNT;

-- Step 2: Check which control files are listed
SHOW PARAMETER control_files;
-- Example output: /u01/oradata/orcl/control01.ctl, /u02/oradata/orcl/control02.ctl

-- Step 3: Exit SQL*Plus and copy the surviving control file to replace the missing one
-- (Perform this at the OS level)

# At the OS prompt, copy the surviving control file
cp /u02/oradata/orcl/control02.ctl /u01/oradata/orcl/control01.ctl

# Verify the copy
ls -la /u01/oradata/orcl/control01.ctl

-- Step 4: Mount and open the database
STARTUP MOUNT;
ALTER DATABASE OPEN;

-- Step 5: Verify all control files are healthy
SELECT name, status FROM v$controlfile;

3. Remove a Missing Control File from CONTROL_FILES (If Multiplexing Allows It)

If one control file is permanently lost but others survive, and you cannot restore the missing one:

-- Step 1: Start NOMOUNT
STARTUP NOMOUNT;

-- Step 2: Modify CONTROL_FILES to remove the missing file path
-- If using spfile:
ALTER SYSTEM SET control_files =
  '/u02/oradata/orcl/control02.ctl',
  '/u03/oradata/orcl/control03.ctl'
SCOPE=SPFILE;

-- Step 3: Restart to pick up the new parameter
SHUTDOWN ABORT;
STARTUP;

-- Step 4: After opening, re-add a new multiplexed copy
ALTER DATABASE BACKUP CONTROLFILE TO '/u01/oradata/orcl/control01.ctl';

-- Step 5: Update CONTROL_FILES to include the new copy
ALTER SYSTEM SET control_files =
  '/u01/oradata/orcl/control01.ctl',
  '/u02/oradata/orcl/control02.ctl',
  '/u03/oradata/orcl/control03.ctl'
SCOPE=SPFILE;

-- Step 6: Bounce the database to make the new multiplexing effective
SHUTDOWN IMMEDIATE;
STARTUP;

4. Restore Control File from RMAN Backup

If all control files are lost or corrupted:

# Step 1: Start RMAN and connect to the target (NOMOUNT state)
rman target /

# Step 2: Start the instance in NOMOUNT
RMAN> STARTUP NOMOUNT;

# Step 3: Restore the control file from the most recent RMAN backup
RMAN> RESTORE CONTROLFILE FROM AUTOBACKUP;

# If the autobackup location is not the default, specify it:
RMAN> RESTORE CONTROLFILE FROM '/u03/backup/orcl/c-12345678-20260323-00';

# Step 4: Mount the database with the restored control file
RMAN> ALTER DATABASE MOUNT;

# Step 5: Recover the database (necessary after control file restore)
RMAN> RECOVER DATABASE;

# Step 6: Open with RESETLOGS
RMAN> ALTER DATABASE OPEN RESETLOGS;

5. Recreate Control File Manually (Last Resort)

If no backup exists and no multiplexed copies survive, recreate the control file manually. This requires knowing all datafile and redo log locations:

-- Step 1: Start in NOMOUNT
STARTUP NOMOUNT;

-- Step 2: Recreate the control file
-- Use NORESETLOGS if redo logs are intact; RESETLOGS if they are not
CREATE CONTROLFILE REUSE DATABASE "ORCL"
  NORESETLOGS ARCHIVELOG
  MAXLOGFILES 32
  MAXLOGMEMBERS 3
  MAXDATAFILES 1024
  MAXINSTANCES 8
  MAXLOGHISTORY 292
LOGFILE
  GROUP 1 (
    '/u01/oradata/orcl/redo01a.log',
    '/u02/oradata/orcl/redo01b.log'
  ) SIZE 200M,
  GROUP 2 (
    '/u01/oradata/orcl/redo02a.log',
    '/u02/oradata/orcl/redo02b.log'
  ) SIZE 200M,
  GROUP 3 (
    '/u01/oradata/orcl/redo03a.log',
    '/u02/oradata/orcl/redo03b.log'
  ) SIZE 200M
DATAFILE
  '/u01/oradata/orcl/system01.dbf',
  '/u01/oradata/orcl/sysaux01.dbf',
  '/u01/oradata/orcl/undotbs01.dbf',
  '/u01/oradata/orcl/users01.dbf'
CHARACTER SET AL32UTF8;

-- Step 3: Recover the database
RECOVER DATABASE USING BACKUP CONTROLFILE UNTIL CANCEL;
-- Apply archived logs as prompted, then type CANCEL

-- Step 4: Open with RESETLOGS
ALTER DATABASE OPEN RESETLOGS;

-- Step 5: Create a new TEMP tablespace entry (TEMPFILES are not recorded in control file)
ALTER TABLESPACE temp ADD TEMPFILE '/u01/oradata/orcl/temp01.dbf'
SIZE 4G AUTOEXTEND ON;

6. Verify Recovery Completeness

After any control file recovery:

-- Verify all datafiles are accounted for
SELECT
  file#,
  name,
  status,
  checkpoint_change#
FROM v$datafile
ORDER BY file#;

-- Check for files needing media recovery
SELECT file#, name, status
FROM v$datafile
WHERE status NOT IN ('SYSTEM', 'ONLINE')
ORDER BY file#;

-- Verify redo log groups
SELECT group#, members, status, archived
FROM v$log
ORDER BY group#;

-- Confirm database is open normally
SELECT name, open_mode, db_unique_name
FROM v$database;

Prevention Strategies

1. Always Multiplex Control Files

-- Verify control file multiplexing (should have at least 3 copies on different disks)
SELECT name, status FROM v$controlfile;

-- Add a new multiplexed copy of the control file
-- Step 1: Copy at OS level while database is shut down
-- cp /u01/oradata/orcl/control01.ctl /u03/oradata/orcl/control03.ctl

-- Step 2: Update CONTROL_FILES parameter
ALTER SYSTEM SET control_files =
  '/u01/oradata/orcl/control01.ctl',
  '/u02/oradata/orcl/control02.ctl',
  '/u03/oradata/orcl/control03.ctl'
SCOPE=SPFILE;

-- Step 3: Restart to activate
SHUTDOWN IMMEDIATE;
STARTUP;

2. Configure RMAN Control File Autobackup

-- Enable RMAN control file autobackup
RMAN> CONFIGURE CONTROLFILE AUTOBACKUP ON;
RMAN> CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK
      TO '/u03/backup/%F';

-- Verify the setting
RMAN> SHOW CONTROLFILE AUTOBACKUP;

3. Keep a Current Trace-Based Backup of the Control File

-- Generate a text-based control file backup after any structural change
ALTER DATABASE BACKUP CONTROLFILE TO TRACE;

-- The trace file will be written to the diagnostic trace directory
-- Store this file in a safe location outside the database server

-- Or write directly to a named file
ALTER DATABASE BACKUP CONTROLFILE TO '/u03/backup/orcl/controlfile_bkp.sql';

4. Monitor Control File Health

-- Schedule regular control file health checks
SELECT
  name,
  status,
  block_size,
  file_size_blks
FROM v$controlfile;

-- Alert if any control file status is not expected
SELECT
  CASE WHEN COUNT(*) < 3
    THEN 'WARNING: Fewer than 3 control file copies'
    ELSE 'OK: ' || COUNT(*) || ' control file copies found'
  END AS status
FROM v$controlfile
WHERE status IS NULL OR status = 'VALID';

Diagnostic Scripts

These Oracle Day by Day scripts can assist with storage and database structure analysis:

health.sql — Comprehensive database health check including control file status
db.sql — Database instance and structural information

ORA-01034 - Oracle not available (database not open)
ORA-01109 - Database not open
ORA-01578 - Oracle data block corrupted
ORA-00257 - Archiver error (can prevent clean shutdown before corruption)

Emergency Response

Quick Fixes

Check if a multiplexed copy is available

# Look in all CONTROL_FILES locations from the alert log
ls -la /u01/oradata/orcl/control01.ctl
ls -la /u02/oradata/orcl/control02.ctl
ls -la /u03/oradata/orcl/control03.ctl

Copy a surviving multiplexed control file to replace the missing one
Terminal window
```
cp /u02/oradata/orcl/control02.ctl /u01/oradata/orcl/control01.ctl
```

Restore from RMAN autobackup if no copies survive

rman target /
RMAN> STARTUP NOMOUNT;
RMAN> RESTORE CONTROLFILE FROM AUTOBACKUP;
RMAN> ALTER DATABASE MOUNT;
RMAN> RECOVER DATABASE;
RMAN> ALTER DATABASE OPEN RESETLOGS;

Post-Resolution Cleanup

-- Verify all control files are healthy
SELECT name, status FROM v$controlfile;

-- Confirm database opened normally
SELECT name, open_mode FROM v$database;

-- Take a fresh RMAN backup immediately after recovery
-- RMAN> BACKUP DATABASE PLUS ARCHIVELOG;

-- Re-enable RMAN control file autobackup if it was not already set
-- RMAN> CONFIGURE CONTROLFILE AUTOBACKUP ON;

-- Update documentation with the control file paths and multiplexing configuration
SELECT name FROM v$controlfile ORDER BY name;