What does Windows error code 6640 (ERROR_LOG_CONTAINER_WRITE_FAILED) mean?

ERROR_LOG_CONTAINER_WRITE_FAILED

Log service encountered an error when attempting to write to a log container.

ERROR_LOG_CONTAINER_WRITE_FAILED is Win32 error 6640 (0x000019F0) in Common Log File System (CLFS). Interpret this result at the call that produced it and use the system message above as the immediate condition rather than as a complete root cause.

Windows assigns decimal 6640 and hexadecimal 0x000019F0 to this result. The decisive subject is writing data to a CLFS log container; the value alone does not reveal which object, server, file, session, or transition failed.

Where the result appears

• appending a transaction record.
• writing a restart area.
• extending a log into a new container.
• persisting records before a dependent data-file update.

State boundary to prove

This result applies to writing data to a CLFS log container 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 the selected container accepts the requested write and makes the expected bytes available to CLFS. Use container identity and write offset, record length and marshaling sizes, and free space, quota, and allocation status 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 is full or quota constrained.
• the container became read-only or inaccessible.
• the storage stack rejected or partially completed the write.
• a handle or stream mapping became stale.
• file-system corruption prevents allocation or completion.

Diagnostic sequence

1. capture error 6640 immediately at the API boundary and record the operation that was attempted.
2. identify the exact owner of writing data to a CLFS log container, including object generation, server, path, session, replica, or client context.
3. collect container identity and write offset before restarting a service or changing configuration.
4. compare record length and marshaling sizes with the documented or observed precondition.
5. correlate free space, quota, and allocation status 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

• container identity and write offset.
• record length and marshaling sizes.
• free space, quota, and allocation status.
• lower-level I/O completion code.
• whether the dependent operation committed before the log write failed.

Correlate it 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 6640; 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 stop dependent commits, preserve the first I/O status, restore writable storage or capacity, and verify the log before resuming writers.

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_container_write_failed_api for the producing function or management operation.
• record log_container_write_failed_target for the file, log, session, replica, object, or server identity.
• record log_container_write_failed_state_before and log_container_write_failed_requested_transition.
• record log_container_write_failed_first_status for the earliest lower-level diagnostic.

For support escalation involving it, retain decimal 6640, hexadecimal 0x000019F0, 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 means records were appended but durability could not be confirmed; this code means the container write operation itself failed.

Practical validation scenario

A database appends a recovery record while the log volume is at quota. The append fails before the data page is changed; increasing the quota and verifying the container permits a safe retry. 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 6640, hexadecimal 0x000019F0, 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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