Ssis-661 ❲ULTIMATE • 2026❳

She followed the beacon’s vector through shadowed corridors. The lights she brought painted walls with broad, impartial strokes. Each room told a story in objects: a tablet looping a scrawled message of congratulations; a workstation with a single, half-finished model of an orbital filter; a bunk where someone had left a book open mid-sentence. There were no bodies. The station had been evacuated in a hurry, not in a panic. The logs she recovered showed calm directives, then a cutoff.

| # | Root‑cause description | How it triggers SSIS‑661 | |---|------------------------|--------------------------| | 1 | – columns added, removed, data‑type changed, or column order changed in the source object (table, view, query, flat‑file, etc.) after the package was designed. | When the data‑flow component reads the external metadata at run‑time, it discovers a mismatch with the metadata that was cached at design‑time. | | 2 | Package was deployed to a different environment (DEV → TEST → PROD) where the source/target objects have a slightly different definition. | The component still uses the design‑time metadata (e.g., nvarchar(50) ) while the actual column is now nvarchar(100) . | | 3 | Changes in a referenced SSIS project/parameter – a package variable, project parameter, or connection manager property that defines a query or file path was altered without re‑validating the data‑flow. | The component re‑generates external metadata based on the new query/path, which no longer matches the cached metadata. | | 4 | Using a dynamic query (e.g., SELECT * FROM dbo.Table WHERE … ) together with property expressions that change the query at run‑time. | The component cannot predict the resulting schema, so it falls back to the design‑time schema; the runtime schema is different → error. | | 5 | Metadata cache corruption – rare, but can happen after a package is edited in multiple versions of SSDT/VS or after a forced package load without a full validation. | The component reads an inconsistent cached definition and throws SSIS‑661. | | 6 | Incorrect data‑type mapping in a Data Conversion or Derived Column that forces the component to expect a different physical type than the source actually provides. | The component validates metadata and finds a type mismatch. | SSIS-661

And in the shuttle’s log, hidden behind a coded lock, Mara’s last message sat like a small, persistent star: If we become more than ourselves, see us kindly. There were no bodies

| Technique | How to implement | |-----------|-----------------| | | Add an Execute SQL Task that runs SELECT TOP 0 * FROM dbo.Table and checks sys.columns via a script task; raise an error if a mismatch is detected. | | Version‑controlled source objects | Keep a DDL script in source control and enforce a build‑time check that the production object matches the script. | | Explicit column list in all sources | Never use SELECT * . | | Package‑level data‑type constraints | Use the Data Flow → Advanced → Data Type property to lock a column to a specific type. | | Deploy with “ValidateExternalMetadata = False” (cautiously) | In scenarios where you know the schema will change but you want the package to continue, set the property on the component, but be aware you lose early detection. | | Continuous Integration (CI) testing | Add a step in your CI pipeline that runs the package against a test copy of the production database and fails the build on any SSIS‑661 (or other) error. | | # | Root‑cause description | How it

is a known bug that causes the Data Flow Task to crash (or silently drop rows) when a source column containing Unicode characters is mapped to a destination column that is defined as non‑Unicode (e.g., DT_STR ). The issue typically surfaces in SQL Server Integration Services 2016–2022 when the source is Oracle, MySQL, or a flat‑file encoded in UTF‑8/UTF‑16.