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DB_E_UNSUPPORTEDCONVERSION
Meaning
Windows documents DB_E_UNSUPPORTEDCONVERSION as “Requested conversion is not supported”. Here, a consumer requests a source-to-destination OLE DB type conversion that the provider does not support.
Evidence to collect before changing the system
When it involves unconverted values, binary payloads, locale-specific text and parameter data, record types, lengths, hashes or redacted identifiers instead of secrets or full business data.
- Evidence 1: the source and destination DBTYPE values.
- Evidence 2: conversion flags, precision, scale and maximum length.
- Evidence 3: the result of IConvertType::CanConvert on the same object.
Relevant OLE DB contract
This result must be interpreted against this contract: OLE DB separates conversion capability from conversion of a particular value; IConvertType reports supported type routes, while bindings additionally carry length, precision, scale, status and storage semantics.
Start with the provider object performing the conversion and the exact source and destination type description when investigating this result.
Specific conditions that produce it
- Cause 1: IConvertType::CanConvert would report the type pair unsupported.
- Cause 2: the requested flags require long-data or command conversion not implemented by the provider.
- Cause 3: a binding assumes an implicit conversion available in another provider.
Corrective actions
- Action 1: bind using a natively supported type pair.
- Action 2: perform the conversion in consumer code with explicit validation.
- Action 3: negotiate a different column or parameter type before creating the accessor.
Practical incident
A consumer binds a provider-specific binary type directly as a timestamp because another provider accepted it; checking CanConvert and converting explicitly prevents it.
Retry and recovery policy
Retry rule: retry only after changing the type pair or moving conversion to a supported layer.
Difference from related HRESULT values
DB_E_CANTCONVERTVALUE means a supported conversion failed for a particular value, while DB_E_UNSUPPORTEDCONVERSION means the conversion route itself is not supported.
Official Microsoft references
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