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hrTooManyKeys
The object and state that matter
For hrTooManyKeys, the diagnostic value comes from the specific ESE error family and the exact operation that returned it. The decisive boundary is an index definition contains more key segments than the engine accepts.
This result is the legacy Directory Service backup/restore HRESULT form of the ESE condition normally written as JET_errTooManyKeys. Preserve the original value 0xC80003F8 when a wrapper also exposes a signed JET_ERR.
The key comparison for this HRESULT is this: hrIndexInvalidDef covers other malformed definitions; this result isolates segment count. The first useful observation is to preserve the complete key definition string, segment order, sort direction, and conditional columns. This it evidence separates index schema, current-index cursor state, key construction, and duplicate data.
Minimum useful trace
A useful trace for this HRESULT should preserve the first failing operation and the state of the B-tree index definition, key construction, uniqueness, and current-index cursor state.
- Code-specific observation: preserve the complete key definition string, segment order, sort direction, and conditional columns.
- the current index plus every JetMakeKey segment and grbit; associate it with this result rather than with a later generic exception.
- the encoded key and existing row when uniqueness is involved; associate it with this result rather than with a later generic exception.
- the raw index key definition, flags, locale, and conditional columns; associate it with it rather than with a later generic exception.
Log lengths, hashes, IDs, flags, and redacted samples where appropriate.
How to avoid a false diagnosis
For this HRESULT, hrIndexInvalidDef covers other malformed definitions; it isolates segment count. The following neighboring results belong to the same broad subsystem but mark different boundaries:
hrTooManyIndexes | a table schema attempted to exceed the supported number of indexes |
|---|---|
hrIndexCantBuild | ESE cannot construct the requested clustered index from the existing table and definition |
hrNullKeyDisallowed | an index definition or inserted row produces a null key where the index contract forbids it |
Keep it in the incident record; replacing it with “database error” hides whether the next step is handle renewal, schema correction, lock reconciliation, or file preservation.
The ESE objects in play
| Diagnostic layer | B-tree index definition, key construction, uniqueness, and current-index cursor state |
|---|---|
| Typical API surface | JetCreateIndex, JetDeleteIndex, JetSetCurrentIndex, JetMakeKey, JetSeek, and JetSetIndexRange |
| Code-specific boundary | an index definition contains more key segments than the engine accepts |
| First corrective direction | reduce key segments or replace part of the key with filtering in application logic |
Index schema and runtime key-building state are separate diagnostic layers., key bytes depend on segment order, column representation, collation, null rules, and sort direction.
Safe recovery sequence
- Freeze the failing request context and record it,
0xC80003F8, the Jet API name, and the current instance/session ownership. - Verify the code-specific precondition: preserve the complete key definition string, segment order, sort direction, and conditional columns.
- Apply the narrow correction: reduce key segments or replace part of the key with filtering in application logic.
- Before retrying it, reconcile index definition, selected cursor index, and key or uniqueness outcome.
- repeat the smallest read-only or disposable test that exercises the corrected precondition; then confirm both the returned HRESULT and the resulting database, cursor, or file state.
Developer-facing acceptance test
Build a focused test that reproduces it at the B-tree index definition, key construction, uniqueness, and current-index cursor state layer. Record the precondition, execute one API call, and assert the HRESULT plus the resulting handle and transaction state. The corrected it test should change only the decisive condition—an index definition contains more key segments than the engine accepts—and should prove that cleanup is safe if the call still fails.
Actions that can hide or worsen the problem
- do not drop or rebuild an index before checking uniqueness and table-layout dependencies.
- do not treat a key-construction or duplicate-key result as database-file corruption.
Technical references
- JetCreateIndex — used to verify the ESE object model, API ordering, or error family relevant to it.
- JetMakeKey
- JetSeek
- ESE source repository
- Microsoft: JET_ERR enumeration
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