What does Windows error code 157 (ERROR_DISCARDED) mean?

ERROR_DISCARDED

What ERROR_DISCARDED means

ERROR_DISCARDED is Win32 system error code associated with the documented message: “The segment is already discarded and cannot be locked.” The significant condition is that a movable legacy memory segment has already been discarded, so a later lock request has no backing storage to pin.

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

Likely causes

• a 16-bit component retained a stale selector or segment handle after memory pressure
• cleanup discarded a movable segment while another path still expected to lock it
• an emulator or compatibility layer exposed lifecycle behavior that the old application did not anticipate

Troubleshooting steps

1. Capture the segment handle at allocation, discard, and lock points
2. Verify whether the failure occurs only after memory pressure or task switching
3. Test the component in the intended compatibility subsystem and compare its segment-lifetime trace

Code-specific investigation notes

A discarded movable segment has lost its backing contents but may still be represented by a handle. Code that treats the handle alone as proof of valid storage can therefore fail later.

Look for memory-pressure callbacks and discardable-resource policies in addition to explicit discard calls. The segment may have been released by the compatibility memory manager.

A correct repair re-establishes the data or prevents premature discard; repeatedly locking the stale handle cannot reconstruct the segment contents.

Example

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_LOCKED says a segment is still locked and cannot be reallocated; it is the opposite lifecycle problem—the segment contents are already gone when code tries to lock them.

References

• Microsoft: System error codes 0–499