What does HRESULT 0x00040EC1 (DB_S_COLUMNTYPEMISMATCH) mean?

DB_S_COLUMNTYPEMISMATCH

OLE DB copy detected incompatible column types

DB_S_COLUMNTYPEMISMATCH is HRESULT 265921 (0x00040EC1) from Microsoft OLE DB. The documented description is “One or more column types are incompatible; Conversion errors will occur during copying.” The high-order severity bit is clear, so this is a success result, but it carries more information than plain S_OK.

The copy or transfer operation continued, but one or more source and destination column types are incompatible and conversions can fail.

Where the result is encountered

• This result can appear in rowset copy operations; record the producing interface and method.
• This result can appear in schema migration through OLE DB; record the producing interface and method.
• It can appear in bulk transfer between providers with different type systems; record the producing interface and method.

Diagnostic sequence

• Capture the raw HRESULT 0x00040EC1 immediately after the returning method and record whether the caller used SUCCEEDED, FAILED, equality testing, or exception translation.
• Verify the method-specific state: each column mapping is inspected and conversion status is checked before the destination is considered complete.

State to verify

The central question is whether each column mapping is inspected and conversion status is checked before the destination is considered complete.

Correct handling, retry, and recovery

Correct mappings or add explicit conversions. If partial copying is allowed, quarantine rows with conversion errors and reconcile counts before commit.

Evidence to preserve

• Preserve source and destination metadata.
• Preserve ordinal mapping.
• Preserve DBTYPE values, precision, scale, and length.
• Preserve per-column status values.
• Preserve rows rejected or truncated during conversion.

Difference from nearby HRESULT values

DB_S_TYPEINFOOVERRIDDEN says caller-supplied parameter metadata replaced provider inference; it identifies incompatible mapped columns.

Developer and administrator guidance

Practical validation scenario

A migration copies a Unicode identifier into a narrow numeric destination column. The provider warns before conversion; the tool changes the schema mapping and reruns in a transaction.

References

• Microsoft: OLE DB return codes
• Microsoft: OLE DB Driver return codes
• Microsoft: OLE DB error records