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UTC_E_ALTERNATIVE_TRACE_CANNOT_PREEMPT
Interpret the result in context: trace-priority arbitration
When UTC_E_ALTERNATIVE_TRACE_CANNOT_PREEMPT (0x87C51002) is returned, the producing layer is ETW trace-session control for it. Start by locating the exact scenario-engine boundary that emitted this Value. The rejected object or state is trace-priority arbitration, and the specific boundary is that a lower-priority alternative profile attempted to replace a trace that owns the exclusive slot for it. Later service errors should not replace this first result in the incident record for it.
The Universal Telemetry Client controls ETW sessions on behalf of diagnostic scenarios for it. ETW sessions have controller-owned names, in-memory buffers, providers, logging modes and lifetimes; a status at this layer should be correlated with the actual session list rather than inferred from the presence of an ETL file for it. Record the configuration package or scenario generation together with the Windows build; otherwise a repaired file can be tested against a stale in-memory graph and appear to fail for the same reason for it.
Build a minimal evidence set
| UTC diagnostic field | Value |
|---|---|
| Owning state or object | trace-priority arbitration |
| Producing layer | ETW trace-session control |
| Do not confuse with | UTC_E_EXCLUSIVITY_NOT_AVAILABLE rejects a new exclusive trace even when it is not an alternative-toggle operation |
| Decisive evidence | active session/profile names, both priorities, exclusivity flags, controller PID and start times |
| Narrow comparison | stop the higher-priority trace in a controlled test and retry the lower-priority profile without changing its contents |
The AllStat message names the immediate condition as “Cannot pre-empt running trace: The current trace has a higher priority” for it. In practice, the useful extension is to ask whether the request was rejected before any side effect, after partial setup, or during cleanup for it. Verify the existence and ownership of the expected output—session, directory, process, result object or emitted event—rather than assuming the message describes the final system state for it.
Run an A/B check
- Freeze the failing scenario package, caller inputs and UTC service lifetime that produced this result.
- Collect the high-value state: active session/profile names, both priorities, exclusivity flags, controller PID and start times for it.
- Use a passing control on the same Windows build, then stop the higher-priority trace in a controlled test and retry the lower-priority profile without changing its contents for it.
- Repeat once after normal teardown to prove the result is not caused by a stale handle or leftover run state for it.
The most informative neighbor is UTC_E_EXCLUSIVITY_NOT_AVAILABLE. The distinction is concrete: UTC_E_EXCLUSIVITY_NOT_AVAILABLE rejects a new exclusive trace even when it is not an alternative-toggle operation for it. Keeping both symbolic names in logs prevents a broad “DiagTrack error” bucket from hiding whether the failure occurred during parsing, authorization, resource acquisition, execution or teardown for it.
Trace-session note
Use an ETW controller view to list session name, GUID, mode, buffers and enabled providers while this result is active. The presence of an ETL file from an earlier run is not proof that the required in-memory session currently exists or is owned by UTC for it.
Safe remediation
Schedule the lower-priority capture after the owner exits or redesign the profile so it does not require preemption for it. Apply that change only to the owning boundary for it. A successful repair must make the controlled case cross this boundary while retaining the intended policy, trace providers, destination and security context for it.
Avoid broad registry resets or global service-policy changes until the single-owner comparison has been run for it. They can hide the original configuration generation without proving the contract was corrected for it.
- the same request now produces its documented success or nonfatal status without a second hidden retry
- the operational log shows one coherent request lifetime and no orphaned action, timer, process or trace session
- teardown followed by a second run does not reuse stale state or recreate trace-priority arbitration
- the nearby condition remains distinguishable: UTC_E_EXCLUSIVITY_NOT_AVAILABLE rejects a new exclusive trace even when it is not an alternative-toggle operation
Technical references
- Microsoft Open Specifications: Windows error-code registry — reference for ETW trace-session control while interpreting this result.
- Microsoft: Universal Telemetry Client configuration diagnosis — reference for ETW trace-session control while interpreting this result.
- Microsoft: Event Tracing for Windows — reference for ETW trace-session control while interpreting it.
- Microsoft: WPR and ETW sessions
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