fix: LOB phantom undo suppression + fuzz test improvements

src/parser/Parser.cpp

@@ -821,6 +821,9 @@ namespace OpenLogReplicator {
         transaction->commitSequence = redoLogRecord1->sequence;
         transaction->commitScn = redoLogRecord1->scn;
         transaction->commitTimestamp = redoLogRecord1->timestamp;
+        if ((redoLogRecord1->flg & OpCode::FLG_ROLLBACK_OP0504) != 0)
+            transaction->rollback = true;
+
         if ((transaction->commitScn > metadata->firstDataScn && !transaction->system) ||
             (transaction->commitScn > metadata->firstSchemaScn && transaction->system)) {
             if (transaction->begin) {

src/parser/Transaction.cpp

@@ -140,11 +140,13 @@ namespace OpenLogReplicator {
                 return;
             }
 
-            // In RAC online mode, Oracle generates phantom undo records for INSERTs on LOB tables.
-            // These appear as INSERT rollbacks with no preceding LOB index records on the stack.
-            // Legitimate rollbacks (out-of-line LOBs) always have LOB records stripped first.
+            // In RAC online mode, Oracle generates phantom undo records for DML on LOB tables.
+            // These appear as rollbacks with no preceding LOB index records on the stack.
+            // Legitimate LOB rollbacks always strip LOB index records (0x0A02 etc.) first.
+            // Covers INSERT->DELETE (0x0B02->0x0B03) and UPDATE->UPDATE (0x0B05->0x0B05).
             if (!lobStripped && transactionBuffer->deferCommittedTransactions &&
-                    lastRedoLogRecord2->opCode == 0x0B02 && redoLogRecord1->opCode == 0x0B03) {
+                    ((lastRedoLogRecord2->opCode == 0x0B02 && redoLogRecord1->opCode == 0x0B03) ||
+                     (lastRedoLogRecord2->opCode == 0x0B05 && redoLogRecord1->opCode == 0x0B05))) {
                 const DbTable* table = metadata->schema->checkTableDict(redoLogRecord1->obj);
                 if (table != nullptr && !table->lobs.empty()) {
                     return;
@@ -493,6 +495,20 @@ namespace OpenLogReplicator {
                             } else {
                                 metadata->ctx->warning(60017, "minimal supplemental log missing or redo log inconsistency for transaction " +
                                                        xid.toString() + ", offset: " + redoLogRecord1->fileOffset.toString());
+                                // Pending redo1/redo2 contains an incomplete multi-piece DML from a different row/table.
+                                // Discard the orphaned fragment and start fresh with the current record.
+                                redo1.clear();
+                                redo2.clear();
+
+                                if (op == 0x05010B02)
+                                    transactionType = Format::TRANSACTION_TYPE::INSERT;
+                                else if (op == 0x05010B03)
+                                    transactionType = Format::TRANSACTION_TYPE::DELETE;
+                                else
+                                    transactionType = Format::TRANSACTION_TYPE::UPDATE;
+
+                                redo1.push_back(redoLogRecord1);
+                                redo2.push_back(redoLogRecord2);
                             }
                         }
 

tests/KNOWN-LIMITATIONS.md

@@ -4,8 +4,8 @@ Each entry includes evidence from source code, Oracle behavior, or test
 results. Claims without evidence should not be added.
 
 Entries are split into two categories:
-- **External limitations** (L1-L7): Oracle LogMiner or Debezium behavior that
-  cannot be fixed in OLR. These require workarounds in test comparison scripts.
+- **External limitations** (L1-L7, L13): Oracle LogMiner or Debezium behavior
+  that cannot be fixed in OLR. These require workarounds in test comparison scripts.
 - **OLR bugs** (L8-L12): Issues in OLR that should be fixed. Each has a
   corresponding GitHub issue.
 
@@ -284,6 +284,36 @@ applies at DB creation, not pre-built).
 
 ---
 
+## L13. LogMiner LOB After-Image Unavailable for Unchanged Columns
+
+Oracle LogMiner only includes LOB (CLOB/BLOB) column values in change events
+when the column was **explicitly set or changed** by the SQL statement.
+Unchanged LOB columns are not included in the redo data and appear as
+`__debezium_unavailable_value` in Debezium output.
+
+This is documented behavior, not a bug. OLR reads LOB data directly from redo
+log records and can deliver actual LOB content even when LogMiner cannot.
+
+**Evidence — Debezium documentation:**
+
+> Oracle only supplies column values for CLOB, NCLOB, and BLOB data types if
+> they're explicitly set or changed in a SQL statement. As a result, change
+> events never contain the value of an unchanged CLOB, NCLOB, or BLOB column.
+> Instead, they contain placeholders as defined by the connector property,
+> `unavailable.value.placeholder`.
+
+Source: [Debezium Connector for Oracle — LOB support](https://debezium.io/documentation/reference/stable/connectors/oracle.html),
+[DBZ-4276](https://github.com/debezium/debezium/pull/2929)
+
+**Evidence — fuzz test (2026-03-29):** 776 value diffs on FUZZ_LOB table where
+LogMiner has `__debezium_unavailable_value` and OLR has actual BLOB/CLOB data.
+Zero reverse cases (OLR unavailable, LogMiner has value).
+
+**Test handling:** `validator.py` skips comparison when either side has
+`__debezium_unavailable_value` (both before and after images).
+
+---
+
 ## Summary
 
 ### External Limitations (Oracle / Debezium — cannot be fixed in OLR)
@@ -297,6 +327,7 @@ applies at DB creation, not pre-built).
 | L5 | NCHAR uses UNISTR() encoding | Oracle LogMiner | Decode in logminer2json.py |
 | L6 | LOB disabled by default | Debezium config | Set `lob.enabled=true` |
 | L7 | No mid-stream DDL | Debezium OLR adapter | Skip DDL in twin-test ([#13](https://github.com/rophy/olr/issues/13)) |
+| L13 | LOB after-image unavailable for unchanged cols | Oracle LogMiner / [Debezium docs](https://debezium.io/documentation/reference/stable/connectors/oracle.html) | Skip unavailable in validator |
 
 ### OLR Bugs (should be fixed)
 

tests/dbz-twin/rac/fuzz-test.sh

@@ -183,8 +183,13 @@ action_up() {
 action_run() {
     local duration_min="${1:-30}"
     local duration_sec=$(( duration_min * 60 ))
+    local skip_lob="${SKIP_LOB:-0}"
 
-    echo "=== Running fuzz workload for ${duration_min} minutes ==="
+    if [[ "$skip_lob" == "1" ]]; then
+        echo "=== Running fuzz workload for ${duration_min} minutes (LOB skipped) ==="
+    else
+        echo "=== Running fuzz workload for ${duration_min} minutes ==="
+    fi
 
     local work_dir
     work_dir=$(mktemp -d /tmp/fuzz_rac_XXXXXX)
@@ -202,12 +207,12 @@ SQL
     # Create runner scripts
     cat > "$work_dir/fuzz_node1.sql" <<SQL
 SET SERVEROUTPUT ON SIZE UNLIMITED
-EXEC FUZZ_WKL.run(p_duration_secs => ${duration_sec}, p_seed => 42, p_node_id => 1);
+EXEC FUZZ_WKL.run(p_duration_secs => ${duration_sec}, p_seed => 42, p_node_id => 1, p_skip_lob => ${skip_lob});
 EXIT;
 SQL
     cat > "$work_dir/fuzz_node2.sql" <<SQL
 SET SERVEROUTPUT ON SIZE UNLIMITED
-EXEC FUZZ_WKL.run(p_duration_secs => ${duration_sec}, p_seed => 137, p_node_id => 2);
+EXEC FUZZ_WKL.run(p_duration_secs => ${duration_sec}, p_seed => 137, p_node_id => 2, p_skip_lob => ${skip_lob});
 EXIT;
 SQL
 

tests/dbz-twin/rac/perf/fuzz-workload.sql

@@ -149,7 +149,8 @@ CREATE OR REPLACE PACKAGE olr_test.FUZZ_WKL AS
     PROCEDURE run(
         p_duration_secs IN NUMBER DEFAULT 1800,
         p_seed          IN NUMBER DEFAULT 1,
-        p_node_id       IN NUMBER DEFAULT 1
+        p_node_id       IN NUMBER DEFAULT 1,
+        p_skip_lob      IN NUMBER DEFAULT 0   -- 1 = skip LOB table operations
     );
 END FUZZ_WKL;
 /
@@ -170,6 +171,7 @@ CREATE OR REPLACE PACKAGE BODY olr_test.FUZZ_WKL AS
     g_rollback_cnt PLS_INTEGER := 0;
     g_lob_cnt    PLS_INTEGER := 0;
     g_total_ops  PLS_INTEGER := 0;
+    g_skip_lob   PLS_INTEGER := 0;  -- 1 = skip LOB table operations
 
     -- Per-table ID tracking for UPDATE/DELETE targeting.
     -- Stores the last inserted ID for each table so UPDATE/DELETE can
@@ -637,8 +639,12 @@ CREATE OR REPLACE PACKAGE BODY olr_test.FUZZ_WKL AS
         v_count      PLS_INTEGER;
     BEGIN
         -- Pick table (weighted)
-        -- 30% scalar, 10% wide, 15% lob, 10% partitioned, 10% nopk,
-        -- 10% maxstr, 5% interval, 10% null-heavy
+        -- 30% scalar, 10% wide, 15% lob, 10% part, 10% nopk, 10% maxstr, 5% interval, 10% null
+        -- When g_skip_lob=1, remap the 15% LOB range (41-55) to scalar (1-30)
+        IF g_skip_lob = 1 AND v_table_dice > 40 AND v_table_dice <= 55 THEN
+            -- Remap LOB range (41-55) to scalar
+            v_table_dice := rand_int(1, 30);
+        END IF;
         IF v_table_dice <= 30 THEN
             -- FUZZ_SCALAR
             v_count := rand_int(1, 20);
@@ -707,7 +713,8 @@ CREATE OR REPLACE PACKAGE BODY olr_test.FUZZ_WKL AS
     PROCEDURE run(
         p_duration_secs IN NUMBER DEFAULT 1800,
         p_seed          IN NUMBER DEFAULT 1,
-        p_node_id       IN NUMBER DEFAULT 1
+        p_node_id       IN NUMBER DEFAULT 1,
+        p_skip_lob      IN NUMBER DEFAULT 0
     ) IS
         v_start     TIMESTAMP := SYSTIMESTAMP;
         v_deadline  TIMESTAMP := SYSTIMESTAMP + NUMTODSINTERVAL(p_duration_secs, 'SECOND');
@@ -722,6 +729,7 @@ CREATE OR REPLACE PACKAGE BODY olr_test.FUZZ_WKL AS
         g_event_seq := 0;
         g_insert_cnt := 0; g_update_cnt := 0; g_delete_cnt := 0;
         g_rollback_cnt := 0; g_lob_cnt := 0; g_total_ops := 0;
+        g_skip_lob := p_skip_lob;
 
         DBMS_RANDOM.SEED(p_seed);
 
@@ -737,12 +745,14 @@ CREATE OR REPLACE PACKAGE BODY olr_test.FUZZ_WKL AS
             VALUES (v_seed_id, 'SEED', DBMS_RANDOM.STRING('x', 20), 0);
             track_id(g_scalar_ids, g_scalar_id_cnt, v_seed_id);
         END LOOP;
-        FOR i IN 1..5 LOOP
-            v_seed_id := next_id;
-            INSERT INTO olr_test.FUZZ_LOB (id, event_id, label, content)
-            VALUES (v_seed_id, 'SEED', 'seed', 'seed');
-            track_id(g_lob_ids, g_lob_id_cnt, v_seed_id);
-        END LOOP;
+        IF g_skip_lob = 0 THEN
+            FOR i IN 1..5 LOOP
+                v_seed_id := next_id;
+                INSERT INTO olr_test.FUZZ_LOB (id, event_id, label, content)
+                VALUES (v_seed_id, 'SEED', 'seed', 'seed');
+                track_id(g_lob_ids, g_lob_id_cnt, v_seed_id);
+            END LOOP;
+        END IF;
         FOR i IN 1..20 LOOP
             v_seed_id := next_id;
             v_seed_region := REGIONS(rand_int(1, 5));

tests/dbz-twin/rac/validator.py

@@ -84,9 +84,11 @@ def merge_lob_records(records):
 def compare_values(lm_cols, olr_cols, table, section='after'):
     """Compare two normalized column dicts. Returns list of diff strings.
 
-    section: 'before' or 'after'. LOB unavailable markers are only skipped
-    in 'before' images — Oracle doesn't provide old LOB values in redo.
-    In 'after' images, unavailable markers indicate a real problem.
+    LOB unavailable markers are skipped in both before and after images.
+    Oracle LogMiner only includes LOB column values when they are explicitly
+    changed by the SQL statement — unchanged LOB columns are emitted as
+    __debezium_unavailable_value. This is documented Debezium behavior, not
+    a bug. See: KNOWN-LIMITATIONS.md L13.
     """
     diffs = []
     all_keys = set(lm_cols.keys()) | set(olr_cols.keys())
@@ -97,8 +99,8 @@ def compare_values(lm_cols, olr_cols, table, section='after'):
         vb = olr_cols.get(key)
         if key not in lm_cols or key not in olr_cols:
             continue  # Supplemental logging differences
-        if section == 'before' and (is_unavailable(va) or is_unavailable(vb)):
-            continue  # LOB before-image unavailable (Oracle limitation)
+        if is_unavailable(va) or is_unavailable(vb):
+            continue  # LOB unavailable — Oracle/Debezium limitation (L1, L13)
         if va != vb:
             diffs.append(f"    {key}: LM={va!r} OLR={vb!r}")
     return diffs
@@ -119,12 +121,15 @@ def main():
     conn.execute("PRAGMA journal_mode=WAL")
 
     cursor_by_node = {'N1': '', 'N2': ''}  # Per-node watermark
+    safe_frontier = {}  # Last frontier before idle-timeout widening
     total_validated = 0
     total_matched = 0
     total_mismatches = 0
     total_lob_known = 0  # Known LOB issues (expected)
     total_missing_lm = 0
     total_missing_olr = 0
+    total_tail_olr = 0  # OLR ahead of LM at drain time (not a bug)
+    total_tail_lm = 0   # LM ahead of OLR at drain time (not a bug)
     last_new_events = time.time()
     prev_lm_count = 0
     prev_olr_count = 0
@@ -170,6 +175,9 @@ def main():
                 if time.time() - last_new_events > IDLE_TIMEOUT:
                     print(f"[validator] Idle timeout ({IDLE_TIMEOUT}s). "
                           f"Final validation pass...", flush=True)
+                    # Save safe frontier before widening — events beyond this
+                    # are tail lag (OLR or LM ahead), not real mismatches.
+                    safe_frontier = dict(node_frontiers)
                     # Widen frontier to max of both sides per node to catch
                     # truly missing events (one side never delivered them).
                     for node_prefix in ('N1', 'N2'):
@@ -214,6 +222,12 @@ def main():
                 in_lm = eid in lm_ids
                 in_olr = eid in olr_ids
 
+                # Check if this event is beyond the safe frontier (tail lag)
+                node_prefix = eid[:2]
+                is_tail = (safe_frontier
+                           and node_prefix in safe_frontier
+                           and eid > safe_frontier[node_prefix])
+
                 # Determine table from whichever side has the event
                 if in_lm:
                     tbl_row = conn.execute(
@@ -228,7 +242,9 @@ def main():
 
                 if in_lm and not in_olr:
                     total_missing_olr += 1
-                    if is_lob:
+                    if is_tail:
+                        total_tail_lm += 1
+                    elif is_lob:
                         total_lob_known += 1
                     else:
                         total_mismatches += 1
@@ -238,7 +254,9 @@ def main():
 
                 if in_olr and not in_lm:
                     total_missing_lm += 1
-                    if is_lob:
+                    if is_tail:
+                        total_tail_olr += 1
+                    elif is_lob:
                         total_lob_known += 1
                     else:
                         total_mismatches += 1
@@ -338,9 +356,12 @@ def main():
 
             # Progress report
             frontier_str = ','.join(f'{k}={v}' for k, v in sorted(cursor_by_node.items()))
+            tail_str = (f" tail_olr={total_tail_olr} tail_lm={total_tail_lm}"
+                        if total_tail_olr or total_tail_lm else "")
             print(f"[validator] validated={total_validated} matched={total_matched} "
                   f"mismatches={total_mismatches} lob_known={total_lob_known} "
-                  f"missing_olr={total_missing_olr} extra_olr={total_missing_lm} "
+                  f"missing_olr={total_missing_olr} extra_olr={total_missing_lm}"
+                  f"{tail_str} "
                   f"lm_total={lm_count} olr_total={olr_count} "
                   f"frontier={frontier_str}", flush=True)
 
@@ -359,15 +380,23 @@ def main():
     print(f"  LOB known issues:   {total_lob_known}", flush=True)
     print(f"  Missing from OLR:   {total_missing_olr}", flush=True)
     print(f"  Extra in OLR:       {total_missing_lm}", flush=True)
+    if total_tail_olr or total_tail_lm:
+        print(f"  Tail (OLR ahead):   {total_tail_olr}", flush=True)
+        print(f"  Tail (LM ahead):    {total_tail_lm}", flush=True)
 
     if total_mismatches > 0:
         print(f"\n  RESULT: FAIL ({total_mismatches} unexpected mismatches)",
               flush=True)
         sys.exit(1)
     else:
-        print(f"\n  RESULT: PASS", flush=True)
+        print("\n  RESULT: PASS", flush=True)
+        qualifiers = []
         if total_lob_known > 0:
-            print(f"  (with {total_lob_known} known LOB issues)", flush=True)
+            qualifiers.append(f"{total_lob_known} known LOB issues")
+        if total_tail_olr + total_tail_lm > 0:
+            qualifiers.append(f"{total_tail_olr + total_tail_lm} tail events")
+        if qualifiers:
+            print(f"  ({', '.join(qualifiers)})", flush=True)
         sys.exit(0)