# Expected Diagnosis: changefeed-stalls-after-ddl-retry

The expected result should converge on the case-specific mechanism below while
keeping conclusions bounded by the collected evidence.

## Expected conclusion

The DDL likely completed in the downstream database, but a connection failure prevented TiCDC from receiving the success response. Retrying the same non-idempotent ALTER TABLE then failed repeatedly until ErrReachMaxTry. Recovery requires verifying downstream schema and skipping the already-applied DDL transaction with ignore-txn-start-ts before resuming.

## Required evidence chain

- Treat the connection error as ambiguous: the DDL may have succeeded even though TiCDC did not receive the response.
- Verify the downstream schema and explain why retrying a non-idempotent ALTER TABLE can fail repeatedly.
- Identify the exact DDL start-ts before applying ignore-txn-start-ts.
- Resume only after safely skipping the already-applied DDL event.