CVssWriter::OnThaw method (vswriter.h)

The OnThaw method is called by a writer following a Thaw event.

OnThaw is a pure virtual method. It is not implemented by the CVssWriter base class, and must be implemented by derived classes.


Platform::Boolean OnThaw();

Return value

The implementation of this method must return true except in the case of a fatal error. If a fatal error occurs, the method must call the CVssWriter::SetWriterFailure method to provide a description of the failure before returning false. If a nonfatal error occurs, the method should still call SetWriterFailure but return true. If the error is caused by a transient problem, the method should specify VSS_E_WRITERERROR_RETRYABLE in the call to SetWriterFailure.

In all cases when a failure occurs, the method should write an event to the event log to report the exact reason for the failure.


This method is called at the end of a shadow copy freeze when writers can begin to modify data on disk again.

OnThaw is used to return the writer to normal operation, typically reversing actions taken during CVssWriter::OnPrepareSnapshot and CVssWriter::OnFreeze.

Final updates by the writer to the backup components metadata and cleanup (such as removing temporary files) are typically reserved for CVssWriter::OnPostSnapshot.

Writers should never throw an exception from this method or any other CVssWriter(Ex)::OnXxx callback method.

If this method calls the CVssWriterEx2::GetSessionId, CVssWriter::SetWriterFailure, or CVssWriterEx2::SetWriterFailureEx method, it must do so in the same thread that called this method. For more information, see Writer Event Handling.


Minimum supported client Windows XP [desktop apps only]
Minimum supported server Windows Server 2003 [desktop apps only]
Target Platform Windows
Header vswriter.h (include Vss.h, VsWriter.h)
Library VssApi.lib

See also