Which two statements about the background process of thedatabase writerare true（）
A. It is possible to have multiple database writers in an Oracle instance.
B. It writes dirty buffers， if any， to data files whenever a checkpoint occurs.
C. It writes dirty buffers， if any， to data files whenever a transaction commits.
D. It writes dirty buffers， if any， to data files before the log writer （LGWR） writes.
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