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--- title: "CMU-15445 SEP042024" type: concept related: [Dbms Storage Management, Dbms Storage Layer] source: https://www.jemoka.com/posts/kbh15445/ confidence: high status: active --- Disk based architecture the DBMS primarily stores stuff on non-violatle disk meaning: the DBMS’ job is to move stuff between violatle and non-volatle storage Challenges how do you makue sure memory-writtten info is commited to disk? Hierarchy model there’s a tradeoff because as your system because faster, you have less of it and (in case its volatle) it stays around less long Access Order Key challenge: random-access on non-volatile storage is almost always slower than sequential access Good DBMS algorithms tries to reduce writes to random pages so stuff is in continuous blocks. Subchapters DBMS Storage Format DBMS Storage Management Overall DBMS Goals We should manage databases that’s larger than memory available We should limit reading/writing to disk We should minimize random accesses Lifetime of a request execution engine asks for a page, say page 2 memory asks its directory for where page 2 is memory found it missing, so ask disk for page 2 disk loads page 2 into memory page 2 memory gives execution engine a pointer to memory