數據庫緩沖池

When several blocks need to be transferred from disk to main memory and all the block addresses are known, several buffers can be reserved in main memory to speed up the transfer.

當需要將幾個塊從磁盤傳輸到主存儲器并且所有塊地址已知時，可以在主存儲器中保留幾個緩沖區以加快傳輸速度。

When one buffer is being used for reading or writing, at that time the CPU can process data in the other buffer because an independent disk (I/O) processor (controller) exists when once it started it can proceed to transfer a block of data between memory and disk independent of and in parallel to CPU processing.

當一個緩沖區用于讀取或寫入時，那時CPU可以處理另一緩沖區中的數據，因為一旦啟動它就存在一個獨立的磁盤(I / O)處理器(控制器)，它就可以繼續傳輸數據塊在內存和磁盤之間獨立于CPU處理并與之并行。

How two processed in parallel are shown in the following figure?

下圖顯示了如何并行處理兩個？

In the above figure Processes, A and B are running concurrently in an interleaved fashion whereas processes C and D are running concurrently in a parallel fashion.

在上圖中，進程A和B以交錯方式同時運行，而進程C和D以并行方式同時運行。

When single processes control multiple processes,parallel execution is not possible.

當單個進程控制多個進程時，無法并行執行。

However, the process can still run concurrently in an interleaved way. Buffering is most useful when processes can run concurrently in parallel fashion, either because a separate disk I/O processor is available or because multiple CPU processors exist.

但是，該過程仍可以以交錯方式并發運行。 當進程可以并行方式并行運行時，緩沖是最有用的，這是因為可以使用單獨的磁盤I / O處理器，或者因為存在多個CPU處理器。

The following figure basically illustrates how reading and processing can proceed in parallel when the time required to process a disk block in memory is less than the time required to read the next block and fill a buffer.

下圖基本說明了在內存中處理磁盤塊所需的時間少于讀取下一個塊并填充緩沖區所需的時間時，如何并行進行讀取和處理。

Processing of CPU starts when the transfer of a block of data to main memory is completed and at the same time next block where the disk I/O processor reading or writing will transfer this block to the different buffer.

當一個數據塊到主存儲器的傳輸完成時，CPU的處理開始，與此同時，磁盤I / O處理器讀取或寫入的下一個塊會將這個塊傳輸到另一個緩沖區。

This technique is basically known as Double Buffering and it is basically used to read a continuous stream of blocks of data from disk to memory.

這種技術基本上被稱為雙緩沖，并且基本上用于從磁盤到內存讀取連續的數據塊流。

Double Buffering permits continuous reading or writing of data on consecutive disk on consecutive disk blocks, which eliminates the seek time and rotational delay for all but the first block transfer.

Double Buffering允許連續讀取或寫入連續磁盤塊上連續磁盤上的數據，從而消除了除了第一個塊傳輸之外的所有磁盤的尋道時間和旋轉延遲。

The most important thing in this is that the data is always ready for processing which helps in reducing the waiting time.

最重要的是，數據始終準備就緒，可以進行處理，這有助于減少等待時間。

翻譯自: https://www.includehelp.com/dbms/buffering-of-blocks.aspx

數據庫緩沖池

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