等待時間描述:

Waiting for a log switch because the session cannot wrap into the next log. Wrapping cannot be performed because the checkpoint for that log has not completed.

當你的日誌組都寫完以後，LGWR 試圖寫第一個log file，如果這時資料庫沒有完成寫出記錄在第一個log file 中的dirty 塊時(例如第一個檢查點未完成)，該等待事件出現。此時online log狀態全部是active狀態

該等待事件通常表示你的DBWR 寫出速度太慢或者IO 存在問題或者正在執行批次插入作業

Top 5 Timed Events

Event	Waits	Time(s)	Avg Wait(ms)	% Total Call Time	Wait Class
log file switch (checkpoint incomplete)	135,745	127,851	942	52.1	Configuration
enq: SQ - contention	12,964	36,530	2,818	14.9	Configuration
read by other session	1,123,797	17,965	16	7.3	User I/O
db file sequential read	1,036,098	17,535	17	7.1	User I/O
buffer busy waits	19,299	15,912	825	6.5	Concurrency

解決辦法

調整引數db_writer_processes增加額外的DBWR

增加你的日誌組或日誌檔案大小

【等待事件】log file switch (checkpoint incomplete)

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