What does Windows error code 6645 (ERROR_LOG_METADATA_FLUSH_FAILED) mean?

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ERROR_LOG_METADATA_FLUSH_FAILED

Log metadata flush failed.

Windows assigns decimal 6645 and hexadecimal 0x000019F5 to ERROR_LOG_METADATA_FLUSH_FAILED. The decisive subject is persisting CLFS metadata; the value alone does not reveal which object, server, file, session, or transition failed.

The native Value is 6645 (0x000019F5). Preserve this result immediately after the failing Windows call because later logging, cleanup, LDAP, RPC, or file operations can replace the last-error value.

Where the result appears

• finishing a container change.
• updating restart areas.
• closing a log after metadata changes.
• making a log-growth or policy operation durable.

State boundary to prove

This result applies to persisting CLFS metadata and does not by itself prove that the entire server, directory, disk, session, or application is unavailable. The state boundary to prove for this Win32 error is whether updated base-log and container metadata reaches durable storage in the required order. Use metadata operation being committed, flush completion status, and volume and controller events as independent evidence. When evidence for this Win32 error disagrees, preserve timestamps and investigate the transition instead of selecting the most convenient value.

Likely causes

• the volume rejected a flush.
• metadata storage is corrupt or inaccessible.
• the device reported a write-cache or media error.
• the log lost access during the flush.
• a shutdown or failover interrupted the durability barrier.

Diagnostic sequence

1. capture error 6645 immediately at the API boundary and record the operation that was attempted.
2. identify the exact owner of persisting CLFS metadata, including object generation, server, path, session, replica, or client context.
3. collect metadata operation being committed before restarting a service or changing configuration.
4. compare flush completion status with the documented or observed precondition.
5. correlate volume and controller events with the owning application log, CLFS-related System events, storage events, and any transaction or recovery trace.
6. determine whether side effects occurred and verify recovery after changing one responsible condition.

Evidence to collect

• metadata operation being committed.
• flush completion status.
• volume and controller events.
• container changes preceding the failure.
• whether a later reopen validates the metadata.

Correlate this result with the owning application log, CLFS-related System events, storage events, and any transaction or recovery trace. Keep the first detailed status even when a later wrapper translates it to error 6645; the first status often distinguishes transport, authorization, storage, schema, state, and application-integrity causes that share the same final Win32 result.

Handling, retry, and recovery

The recovery objective is to treat durability as unknown, stop further mutations, verify the log on stable storage, repair or restore the coordinated log set, and repeat only after metadata consistency is proven.

Retry it only after the recorded condition changes and completion state is known. Idempotent queries may be repeated after recovery, but mutations require a state check first; backoff cannot repair malformed input, corruption, missing structure, or policy rejection.

Telemetry and support fields

• record log_metadata_flush_failed_api for the producing function or management operation.
• record log_metadata_flush_failed_target for the file, log, session, replica, object, or server identity.
• record log_metadata_flush_failed_state_before and log_metadata_flush_failed_requested_transition.
• record log_metadata_flush_failed_first_status for the earliest lower-level diagnostic.

For support escalation involving it, retain decimal 6645, hexadecimal 0x000019F5, the API, UTC time, target identity, and first subsystem-specific status. Include the smallest reproducible request and evidence that distinguishes this condition from nearby codes. In the context of it, clfs clients can run in user mode or kernel mode, so the same win32 result may be returned through an application wrapper, a service, or a driver-facing management path.

Difference from nearby results

ERROR_LOG_APPENDED_FLUSH_FAILED concerns appended records or reservations; this code concerns the log metadata that describes the log itself.

Practical validation scenario

A container is added and its file is created, but the metadata flush fails during storage failover. The service avoids assuming the addition committed and reopens the log to discover the authoritative container set. The negative test should preserve the responsible condition and reproduce it; the recovery test should change only the identified cause, repeat the same operation, and verify both success and the absence of an unintended partial side effect.

Developer and administrator guidance

Administrators handling it should preserve the complete CLFS set—base log, containers, security metadata, and application checkpoint state—before repair. Developers should never delete or recreate a container merely because its path appears in the error; the owning recovery protocol determines whether that data is still required. Code that exposes it through RPC, JSON, REST, PowerShell, or another protocol should preserve the Win32 domain, decimal 6645, hexadecimal 0x000019F5, and original component diagnostic.

References

• Microsoft: Win32 system error range containing this code — official context relevant to it.
• Microsoft: Common Log File System — official context relevant to it.
• Microsoft: Creating a Log File — official context relevant to it.
• Microsoft: Introduction to CLFS — official context relevant to it.

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