diff --git a/src/storage/tx/ob_trans_part_ctx.cpp b/src/storage/tx/ob_trans_part_ctx.cpp
index 9f88175b0a..59eed8b15f 100755
--- a/src/storage/tx/ob_trans_part_ctx.cpp
+++ b/src/storage/tx/ob_trans_part_ctx.cpp
@@ -7213,10 +7213,9 @@ int ObPartTransCtx::check_status_()
  * purpose:
  * 1) verify transaction ctx is *writable*
  * 2) acquire memtable ctx's ref
- * 3) remember data_scn
+ * 3) alloc data_scn
  */
-int ObPartTransCtx::start_access(const ObTxDesc &tx_desc,
-                                 const ObTxSEQ data_scn)
+int ObPartTransCtx::start_access(const ObTxDesc &tx_desc, ObTxSEQ &data_scn)
 {
   int ret = OB_SUCCESS;
   CtxLockGuard guard(lock_);
@@ -7225,14 +7224,18 @@ int ObPartTransCtx::start_access(const ObTxDesc &tx_desc,
     ret = OB_TRANS_SQL_SEQUENCE_ILLEGAL;
     TRANS_LOG(WARN, "stale access operation", K(ret),
               K_(tx_desc.op_sn), K_(last_op_sn), KPC(this), K(tx_desc));
-  } else if (FALSE_IT(++pending_write_)) {
-  } else if (FALSE_IT(last_scn_ = MAX(data_scn, last_scn_))) {
-  } else if (!first_scn_.is_valid() && FALSE_IT(first_scn_ = last_scn_)) {
-  } else if (tx_desc.op_sn_ != last_op_sn_) {
-    last_op_sn_ = tx_desc.op_sn_;
-  }
-
-  if (OB_SUCC(ret)) {
+  } else {
+    if (!data_scn.is_valid()) {
+      data_scn = tx_desc.inc_and_get_tx_seq(0);
+    }
+    ++pending_write_;
+    last_scn_ = MAX(data_scn, last_scn_);
+    if (!first_scn_.is_valid()) {
+      first_scn_ = last_scn_;
+    }
+    if (tx_desc.op_sn_ != last_op_sn_) {
+      last_op_sn_ = tx_desc.op_sn_;
+    }
     mt_ctx_.inc_ref();
     mt_ctx_.acquire_callback_list();
   }
@@ -7318,14 +7321,13 @@ int ObPartTransCtx::rollback_to_savepoint(const int64_t op_sn,
               K(trans_id_), K(ls_id_), K(busy_cbs_.get_size()));
   } else if (op_sn < last_op_sn_) {
     ret = OB_TRANS_SQL_SEQUENCE_ILLEGAL;
-  } else if (op_sn > last_op_sn_ && last_scn_ <= to_scn) {
-    last_op_sn_ = op_sn;
-    TRANS_LOG(INFO, "rollback succeed trivially", K(op_sn), K(to_scn), K_(last_scn));
-  } else if (op_sn > last_op_sn_ && pending_write_ > 0) {
+  } else if (FALSE_IT(last_op_sn_ = op_sn)) {
+  } else if (pending_write_ > 0) {
     ret = OB_NEED_RETRY;
     TRANS_LOG(WARN, "has pending write, rollback blocked",
               K(ret), K(pending_write_), KPC(this));
-  } else if (FALSE_IT(last_op_sn_ = op_sn)) {
+  } else if (last_scn_ <= to_scn) {
+    TRANS_LOG(INFO, "rollback succeed trivially", K(op_sn), K(to_scn), K_(last_scn));
   } else if (OB_FAIL(rollback_to_savepoint_(from_scn, to_scn))) {
     TRANS_LOG(WARN, "rollback_to_savepoint fail", K(ret),
               K(from_scn), K(to_scn), K(op_sn), KPC(this));
diff --git a/src/storage/tx/ob_trans_part_ctx.h b/src/storage/tx/ob_trans_part_ctx.h
index cb5a47073c..3a24a5966b 100644
--- a/src/storage/tx/ob_trans_part_ctx.h
+++ b/src/storage/tx/ob_trans_part_ctx.h
@@ -733,8 +733,7 @@ public:
    * @data_seq: the sequence_no of current access
    *            new created data will marked with this seq no
    */
-  int start_access(const ObTxDesc &tx_desc,
-                   const ObTxSEQ data_seq);
+  int start_access(const ObTxDesc &tx_desc, ObTxSEQ &data_seq);
   /*
    * end_access - end of txn protected resources access
    */
diff --git a/src/storage/tx/ob_trans_service_v4.cpp b/src/storage/tx/ob_trans_service_v4.cpp
index dcc7c640e8..f02834f329 100755
--- a/src/storage/tx/ob_trans_service_v4.cpp
+++ b/src/storage/tx/ob_trans_service_v4.cpp
@@ -1079,7 +1079,7 @@ int ObTransService::get_write_store_ctx(ObTxDesc &tx,
   int ret = OB_SUCCESS;
   const share::ObLSID &ls_id = store_ctx.ls_id_;
   ObPartTransCtx *tx_ctx = NULL;
-  const ObTxSEQ data_scn = spec_seq_no.is_valid() ? spec_seq_no : tx.inc_and_get_tx_seq(0);
+  ObTxSEQ data_scn = spec_seq_no; // for LOB aux table, spec_seq_no is valid
   ObTxSnapshot snap = snapshot.core_;
   ObTxTableGuard tx_table_guard;
   bool access_started = false;