60题、choose one
When does a database checkpoint occur?
A) When there is an online redo log switch.
B) When the SHUTDOWN ABORT command is issued.
C) When a user session terminates abnormally.
D) When a server process terminates abnorthally.
Answer：A
(解析：日志切换时会发生检查点，目的是把记录在该日志中的事务造成的脏块写入数据文件。来自3组：1015267481)