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ERROR_PAGE_FAULT_COPY_ON_WRITE
A write fault created a private copy of a shared page
ERROR_PAGE_FAULT_COPY_ON_WRITE corresponds to Win32 error value documented as: Page fault was a demand zero fault. The process attempted to modify a copy-on-write mapping, causing Windows to allocate a private page and copy the original contents. This is normal for image sections and shared mappings that permit private modification.
Where the result appears in real systems
- Process startup relocations.
- Mapped image writes.
- Fork-like snapshot mechanisms.
- Profilers measuring private working-set growth.
What to collect before making changes
Capture mapping type, protection flags, virtual address, original section, and resulting private bytes; correlate with image relocation or deliberate writes; inspect unexpected high rates for code that dirties broadly shared data.
Handling and recovery
Allow the fault when private modification is intended. Reduce needless writes to shared pages if memory duplication is excessive, and never change protections merely to suppress the diagnostic status.
What not to infer from this code
Unlike an access violation, this fault is resolved successfully because the mapping explicitly supports copy-on-write semantics.
References
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