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The disk buffer is usually quite small, ranging between 8 MB to 4 GB, and the page cache is generally all unused main memory. While data in the page cache is reused multiple times, the data in the disk buffer is rarely reused. [3] In this sense, the terms disk cache and cache buffer are misnomers; the embedded controller's memory is more ...
When blocks must be allocated to hold pending writes, disk space for the appended data is subtracted from the free-space counter, but not actually allocated in the free-space bitmap. Instead, the appended data are held in memory until they must be flushed to storage due to memory pressure, when the kernel decides to flush dirty buffers , or ...
Pages in the page cache modified after being brought in are called dirty pages. [5] Since non-dirty pages in the page cache have identical copies in secondary storage (e.g. hard disk drive or solid-state drive), discarding and reusing their space is much quicker than paging out application memory, and is often preferred over flushing the dirty pages into secondary storage and reusing their space.
In computer science, a data buffer (or just buffer) is a region of memory used to store data temporarily while it is being moved from one place to another. Typically, the data is stored in a buffer as it is retrieved from an input device (such as a microphone) or just before it is sent to an output device (such as speakers); however, a buffer may be used when data is moved between processes ...
The database is placed in a quiescent state by allowing current active transactions to complete and then flushing modified buffers from cache to the stable database. [7] During a quiesced backup, updating transactions are not permitted and attempts to execute database transactions raise a database exception.
For software backward-compatibility, the extended functions are implemented alongside the original CHS functions, and calls to functions from both sets can be intermixed, even for the same drive, with the caveat that the CHS functions cannot reach past the first 8064 MB of the disk. Some cache drivers flush their buffers when detecting that DOS ...
In computing, cache replacement policies (also known as cache replacement algorithms or cache algorithms) are optimizing instructions or algorithms which a computer program or hardware-maintained structure can utilize to manage a cache of information.
Using memory in this way for the initial capture aims to reduce disk IO. Of course, when a transaction commits, the redo log buffer must be flushed to disk, because otherwise the recovery for that commit could not be guaranteed. The LGWR (Log Writer) process does that flushing. Having a redo log makes it possible to replay SQL statements.