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hrTooManyIO
Why this result matters
hrTooManyIO means the engine reached its outstanding-I/O throttle and refused to queue more storage work.
The stored value is 0xC8000069 (negative JET error -105; -105). Current ESE documentation uses JET_errTooManyIO for the corresponding published JET condition.
The first useful distinction is that the storage subsystem can be healthy but saturated; hrDiskIO means an actual I/O operation failed. Start by capturing queue depth, latency, outstanding reads/writes by file, checkpoint lag, backup concurrency, and storage errors.
Do not confuse it with
This result specifically means that the storage subsystem can be healthy but saturated; hrDiskIO means an actual I/O operation failed. Related values below can appear in the same workflow but require a different response:
hrOutOfThreads | ESE could not start a worker thread needed by the requested operation |
|---|---|
hrFileClose | ESE could not complete the operating-system close of a database, log, temporary, or backup file |
hrInvalidBackupSequence | backup APIs were called in an order that violates the ESE external-backup state machine |
Keep the original constant and hexadecimal value in telemetry. Replacing this result with “backup failed” or “database warning” removes the state information needed to select the next legal API call.
Forensic checklist
- Code-specific observation: capture queue depth, latency, outstanding reads/writes by file, checkpoint lag, backup concurrency, and storage errors.
Objects and state involved
| Diagnostic layer | operating-system file, thread, and asynchronous-I/O resources used by ESE |
|---|---|
| Relevant API surface | database/log file I/O, worker creation, backup reads, and background tasks |
| Code-specific condition | the engine reached its outstanding-I/O throttle and refused to queue more storage work |
| Narrow corrective direction | reduce parallelism and resolve latency before retrying rather than creating an I/O retry storm |
The first lower-level Win32 error is more useful than later cascading ESE failures. Resource exhaustion should be measured at the moment of failure, before retries alter counts.
Actions that can make diagnosis worse
- Do not create unbounded retries under resource pressure.
- Do not discard a close or flush error during cleanup.
Validation after correction
- Record it,
0xC8000069, the API name, the current phase, and all live context or file owners. - Verify the condition by capturing queue depth, latency, outstanding reads/writes by file, checkpoint lag, backup concurrency, and storage errors.
- Apply only the targeted fix: reduce parallelism and resolve latency before retrying rather than creating an I/O retry storm.
Acceptance criteria for a fix
A useful regression test should force the condition “the engine reached its outstanding-I/O throttle and refused to queue more storage work”, call one documented API transition, and assert the exact HRESULT.
Technical references
- ESE error-code table — API ordering, file semantics, warning/error interpretation, or recovery behavior relevant to this HRESULT.
- ESE files
- Open-source ESE implementation
- Microsoft JET_ERR enumeration
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