對checkpoint not completed的理解，checkpoint

對checkpoint not completed的理解，checkpoint

假設資料庫存在兩個日誌組log1和log2，首先，－－>log1-->log2-->log1，此時（log2切換到log1）觸發checkpoint，該checkpoint will flush dirty block to datafile,從而觸發DBWn書寫dirty buffer，等到log1覆蓋的dirty block全部被寫入datafile後才能使用log1（迴圈使用），如果DBWn寫入過慢，LGWR必須等待DBWn完成，則這時會出現“checkpoint not completed！”

別人的回答是

log1-> log2, trigger checkpoint 1
after log2 is full,
log2-> log1, trigger checkpoint 2
but if checkpoint 1 is still not finished, then LGWR must wait. This is "logfile switch (checkpoint incompleted)" event.

我的理解是

1.檢查點完成，才能順利切換。

2.checkpoint1阻塞了log2->log1的切換。

3.沒有可用的redo日誌，會阻塞資料正常使用，這時資料庫是短暫hang住的。（原因如下）

不知道對不對，請高人指正~

Before a change is done in the buffer cache a change vector (file, block, row, value) about this change is written to the redo buffer. First the change of the undo block to be made soon is tracked (L). Then the change is done in the buffer cache (M). Then the change of the table block to be made soon is tracked (N). Then the insert to the table block is done in the buffer cache (O). All actions up to now where done by the server process (P). Finally it returns the control to the client process (Q).

redo無法試用，導致事務不能正常進行。

電腦中的setup was not completed successfully什意思

程式沒有成功完成安裝。
有可能是安裝檔案損壞。也有可能是其他原因。根據你具體的安裝程式名稱百度下吧
 
我的PS用濾鏡液化的時出現The operation couLd not be compLeted是什

自己沒遇到過，也許是跟什麼軟體或者濾鏡發生衝突了吧！