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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 storage, a disk buffer (often ambiguously called a disk cache or a cache buffer) is the embedded memory in a hard disk drive (HDD) or solid-state drive (SSD) acting as a buffer between the rest of the computer and the physical hard disk platter or flash memory that is used for storage. [1]
Hardware implements cache as a block of memory for temporary storage of data likely to be used again. Central processing units (CPUs), solid-state drives (SSDs) and hard disk drives (HDDs) frequently include hardware-based cache, while web browsers and web servers commonly rely on software caching.
In software engineering, in-memory processing is a software architecture where a database is kept entirely in random-access memory (RAM) or flash memory so that usual accesses, in particular read or query operations, do not require access to disk storage. [2]
If present in memory and not privately modified the physical page is shared with file cache or buffer. Shared memory acquired through shm_open. The tmpfs in-memory filesystem; written to swap when paged out. The file cache including; written to the underlying block storage (possibly going through the buffer, see below) when paged out.
In effect, physical main memory becomes a cache for virtual memory, which is in general stored on disk in memory pages. Programs are allocated a certain number of pages as needed by the operating system. Active memory pages exist in both RAM and on disk. Inactive pages are removed from the cache and written to disk when the main memory becomes ...
Similarly, a page frame is the smallest fixed-length contiguous block of physical memory into which memory pages are mapped by the operating system. [1] [2] [3] A transfer of pages between main memory and an auxiliary store, such as a hard disk drive, is referred to as paging or swapping. [4]
SAP HANA, short for 'High Performance Analytic Appliance' is an in-memory, column-oriented, relational database management system written in C, C++: solidDB: Unicom Global 1992 Proprietary Relational with standard SQL support. ODBC and JDBC interfaces. Includes in-memory and on-disk tables in the same engine. Supports high availability. SQL CE