What is cache
Cache is a buffer for data exchange (called: Cache). When a piece of hardware wants to read data , will first summarize the query data from the cache, execute it directly if it exists, and obtain it from the memory if it does not exist. Since cached data is much faster than memory, the role of cache is to help the hardware run faster.
Cache often uses RAM (non-permanent storage that is lost when power is turned off), so after use, the files will still be sent to hard disk and other storage for permanent storage. The largest cache in a computer is a memory stick, and there is also a 16M or 32M cache on the hard disk.
The cache is set up to coordinate the difference in access speed between the CPU and main memory. Generally, the working speed of the CPU is high, but the working speed of the memory is relatively low. In order to solve this problem, a cache is usually used. The access speed of the cache is between that of the CPU and the main memory.
Cache is just to save some external storage data in the memory. Why is it saved in the memory? The variables in all the programs we run are stored in the memory, so if you want to put the value into In memory, it can be stored in variables. Some caches in JAVA are generally implemented through Map collections.
The different roles of cache in different scenarios:
Operating system disk cache ——> Reduce disk mechanical operations.
Database cache——>Reduce file system IO.
Application Cache -> Reduce queries to the database.
Web server cache——>Reduce application server requests.
Client browser cache——>Reduce visits to the website.
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