If you’ve been a DBA long enough, you remember the first time you saw ORA-00600 in your alert log. The reaction is always the same: a moment of panic, followed by the realization that the error message tells you almost nothing useful on its own. ORA-00600 is Oracle’s generic internal error code — it means something unexpected happened inside the Oracle kernel that Oracle didn’t have a specific error code for. It could be a bug, a corrupted block, a resource problem, or an environmental issue. The error itself is not the diagnosis; it’s the starting point.

This post is about how to systematically work through ORA-00600 rather than immediately opening an Oracle SR and waiting.

Understanding the Error Format

ORA-00600: internal error code, arguments: [kdsgrp1], [0], [0], [0], [], [], [], []

The first argument in brackets — [kdsgrp1] in this example — is the most important piece of information. It’s an internal Oracle function or module name that tells you where in the kernel the error originated. Each argument code maps to a specific subsystem:

• kd prefix: kernel data layer (row fetching, block access)
• kc prefix: kernel cache (buffer cache operations)
• ko prefix: kernel object (data dictionary operations)
• kcb prefix: kernel cache buffers
• ksu prefix: kernel services user (session management)
• qk prefix: query kernel (SQL parsing, optimization)

The first argument alone often tells an experienced DBA which category of problem they’re dealing with before any further investigation.

Step 1: Find the Trace File

ORA-00600 always generates a trace file. The alert log entry points you to it:

Errors in file /oracle/diag/rdbms/mydb/mydb1/trace/mydb1_ora_12345.trc
ORA-00600: internal error code, arguments: [kdsgrp1]...

Open the trace file immediately. It contains:

• The full call stack at the time of the error
• The SQL statement being executed
• Session information
• Memory dump (for some error types)
• The Oracle version and patch level

bash

# Find recent trace files
ls -lt $ORACLE_BASE/diag/rdbms/$(hostname)/$(hostname)/trace/*.trc | head -10
# Or use ADRCI (Automatic Diagnostic Repository Command Interface)
adrci> show problem
adrci> show incident
adrci> show tracefile

ADRCI is Oracle’s built-in diagnostic tool. show problem lists all ORA-00600 occurrences grouped by first argument. If the same argument appears 50 times, you have a systematic problem, not a one-off.

Step 2: Search My Oracle Support Before Calling Support

Before opening an SR, search MOS (My Oracle Support) for the specific first argument. The search format:

ORA-600 [kdsgrp1]

MOS has a dedicated ORA-600/ORA-7445 Lookup Tool (Doc ID 153788.1) that cross-references first arguments to known bugs and patches. For most common first arguments, there’s already a known bug with a patch or workaround documented.

The key information to gather before searching:

• Oracle Database version and patch level (SELECT * FROM v$version)
• Operating system and version
• The exact first argument (and second argument if present)
• Whether it’s reproducible or intermittent
• What was happening at the time (specific SQL, specific operation)

Step 3: Check for Block Corruption

Many ORA-00600 errors with kd prefix arguments indicate block corruption. Verify immediately:

sql

-- Check for known corrupt blocks
SELECT * FROM v$database_block_corruption;
-- Run RMAN validation to find corruption
RMAN> VALIDATE DATABASE;
RMAN> VALIDATE DATAFILE 5;  -- specific datafile
-- Check alert log for ORA-01578 alongside ORA-00600
-- These often appear together when block corruption is involved

If corruption is confirmed, your path forward is RMAN block recovery (covered in Blog Post 14). The ORA-00600 is a symptom of the corruption, not a separate problem.

Step 4: Identify the Triggering SQL

The trace file contains the SQL that triggered the error. Capture it and test reproducibility:

sql

-- If you have the SQL text, find it in library cache
SELECT sql_id, sql_text, executions, parse_calls
FROM v$sql
WHERE sql_text LIKE '%distinctive_text_from_trace%';
-- Check if it's a specific table causing problems
-- Try explain plan without executing
EXPLAIN PLAN FOR <your_sql>;
SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY);

If the error is reproducible with a specific SQL on a specific table, the problem is likely a corrupted object or a query optimizer bug triggered by specific data patterns.

The ORA-00600 [kdsgrp1] Specifically

Since this is one of the most common first arguments I encounter, worth addressing directly. kdsgrp1 indicates an error during row fetch in the kernel data layer. Most commonly caused by:

• Index corruption (index points to a row that doesn’t exist)
• Mismatch between index entry and table row
• Bug in specific Oracle versions related to compressed tables or IOTs

sql

-- If a specific table is triggering kdsgrp1, validate its indexes
ANALYZE TABLE schema.table_name VALIDATE STRUCTURE CASCADE;
-- Rebuild suspect indexes
ALTER INDEX schema.index_name REBUILD;
-- If the table itself is corrupted
ANALYZE TABLE schema.table_name VALIDATE STRUCTURE;

In many kdsgrp1 cases I’ve resolved, rebuilding the affected index eliminated the ORA-00600 entirely without any patch application.

When to Open an SR Immediately

Some ORA-00600 scenarios require immediate Oracle Support involvement:

• The error is happening on every query against a specific table and you cannot identify corruption
• The instance is crashing (not just the session)
• The first argument is not found anywhere on MOS
• Multiple different ORA-00600 first arguments are appearing simultaneously (suggests a deeper environmental problem)

When opening the SR, upload the trace file and alert log excerpt. Oracle Support will ask for these immediately — having them ready cuts days off the SR resolution time.