What does Windows error code 212 (ERROR_LOCKED) mean?

ERROR_LOCKED

What ERROR_LOCKED means

ERROR_LOCKED is Win32 system error code associated with the documented message: “The segment is locked and cannot be reallocated.” The significant condition is that a legacy movable memory segment still has an active lock when code attempts to resize or relocate it. Preserve the symbolic name together with the numeric value because older diagnostic tools may display only one form.

The term “segment” here refers to movable memory used by historical Windows and OS/2-style programming models. In a the case, this is not the same as a modern virtual-memory region reported by tools such as VirtualQuery.

Likely causes

• one code path locks the segment but misses the matching unlock
• an error or callback returns early while retaining the lock count
• another task is still using the segment when reallocation begins

Diagnostic procedure

1. trace lock and unlock counts for the segment handle
2. identify the first unmatched lock rather than repeatedly retrying reallocation
3. delay resize until all users release the segment and then verify the handle remains valid

During a this result investigation, capture the first operation returning it. In the result timeline, a later cleanup failure can be easier to notice while no longer describing the original defect. The evidence set for it should record executable path, file version, architecture, Windows build, compatibility settings, and non-secret inputs used by the failing operation.

How to interpret the result in modern software

This result belongs to the 0–499 system-error range, but its wording may describe a historical subsystem. Do not classify it automatically as a current Windows kernel defect. First determine whether the value came directly from GetLastError(), was translated from another status domain, arrived over a protocol, or was stored by an old application. Because it can be propagated through wrappers, a missing producer API leaves translation errors and stale last-error values indistinguishable.

Code-specific investigation notes

Movable-segment locks are commonly reference-counted. Two successful lock calls require two matching unlocks before relocation becomes legal.

Instrument handle identity and lock depth across callbacks; logging only the final reallocation call misses the ownership path.

Never force the count to zero in production code. The remaining holder may still dereference the segment after it has moved.

Developer guidance

Code handling this result should check the exact API return first, copy the last-error value immediately, and avoid intervening calls before logging. If it is raised by a loader or compatibility helper, collect parent-process diagnostics because the child may never initialize its own logger. Validate format-specific fields with an appropriate parser; byte-level edits made only to suppress it can turn a clean rejection into corruption or unsafe execution.

Administrator and support guidance

To recover from this result, prefer a matched trusted binary/configuration set over individual DLL downloads or global compatibility changes. Before replacing an artifact associated with it, retain it and calculate a cryptographic hash. When it is isolated to one account or session, compare mappings, namespaces, environment, current directory, and policy before considering system-wide reinstall.

Example incident

A compatibility component retains a stale segment lifecycle state across an error path. The next memory operation encounters that state and returns it.

Difference from related errors

ERROR_DISCARDED occurs when code tries to lock a segment whose storage has already been discarded; it occurs while storage is still pinned and therefore cannot be moved.

Evidence to collect

• the raw decimal and hexadecimal value corresponding to it
• the exact API, command, or loader action that first produced the result
• paths after normalization and redirection, plus hashes and versions of involved binaries
• process architecture, session identity, compatibility mode, and relevant virtualization details
• a timestamp that can be correlated with application logs, Process Monitor traces, and Windows Event Log

Recovery and verification

A it repair is verified only when the original operation succeeds with equivalent inputs and produces usable output. After correcting it, repeat the action in a fresh process and again in the same workflow to test both stale-state removal and repeatable cleanup. If reboot alone removes it, collect enough evidence to identify which mapping, lock, process, or compatibility state the reboot cleared.

References

• Microsoft: System error codes 0–499

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