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hrTooManyColumns
Diagnostic focus
hrTooManyColumns means a table definition has reached the supported number of columns.
This is the legacy Directory Service backup/restore HRESULT form of JET_errTooManyColumns (0xC8000410).
The key comparison is: hrRecordTooBig is a per-row size problem; this result is a schema object-count limit. The first useful observation is to enumerate fixed, variable, tagged, template-derived, and deleted-but-not-reclaimed definitions. This evidence separates schema definition, row-size accounting, null semantics, multivalue selection, and stale column IDs.
The ESE objects in play
| Diagnostic layer | column schema, row-size accounting, tagged/multivalued storage, and column identifiers |
|---|---|
| Typical API surface | JetAddColumn, JetDeleteColumn, JetSetColumn, JetRetrieveColumn, and JET_COLUMNDEF |
| Code-specific condition | a table definition has reached the supported number of columns |
| First corrective direction | consolidate sparse data into an appropriate representation or redesign the table before adding more columns |
Fixed, variable, tagged, and long-value columns consume row space differently. Column IDs are metadata scoped to a table and should be refreshed after schema changes.
Evidence that resolves the ambiguity
- Code-specific observation: enumerate fixed, variable, tagged, template-derived, and deleted-but-not-reclaimed definitions.
- the complete row-size contribution from fixed, variable, tagged, and long-value data; associate it with this result rather than with a later generic exception.
- JET_COLUMNDEF fields, flags, code page, maximum length, and column ID origin; associate it with this result rather than with a later generic exception.
- the encoded value length, null/empty state, and itag sequence.
Nearby results that mean something different
hrTaggedNotNULL | a tagged-column operation used null semantics that are not valid for this representation or engine version |
|---|---|
hrBadColumnId | the numeric JET_COLUMNID is invalid for the current table schema |
hrRecordTooBig | the assembled row exceeds the record-size budget after fixed, variable, tagged, and key overhead are considered |
A disciplined correction path
- Freeze the failing request context and record
0xC8000410, the Jet API name, and the current instance/session ownership. - Verify the code-specific precondition: enumerate fixed, variable, tagged, template-derived, and deleted-but-not-reclaimed definitions.
- Apply the targeted fix: consolidate sparse data into an appropriate representation or redesign the table before adding more columns.
- Before retrying the operation, reconcile column metadata, row layout, and the exact stored value state.
Actions that can hide or worsen the problem
- Do not alter the column schema in place without a migration and rollback plan.
- Do not collapse null, zero-length data, missing value, and tagged-value deletion into one state.
Technical references
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