Database Systems

Disk-oriented architecture, buffer pools, ARC, pages, indexes, and concurrency — as animated state machines.

Walk the storage stack — disk, catalog, then what to evict.

Enter pathDisk-Oriented DBMS Architecture·0/10 opened

01 · Disk
The machine on disk
A database file is not a spreadsheet. It is 8 KB pages, headers, and a buffer pool that copies pages into frames.
- 1.1·intro
  8 steps
  Disk-Oriented DBMS Architecture
  Open the folder, the .db file, then a slotted page.
- 1.2·intro
  7 steps
  Pages vs Frames
  A page is durable. A frame is a RAM slot that holds one.
02 · Catalog
Names become page ids
CREATE TABLE does not stamp the word “users” into the file. It remembers first_page_id in RAM, then writes a heap page.
- 2.1·intermediate
  1 step
  Tables, Catalog & datadb.db
  CREATE stores first_page_id. INSERT writes hex into datadb.db.
03 · Guard
Who may touch the page
Two locks on a vertical slotted page: short BPM mutex, then PageGuard on the frame. UPDATE and INSERT both pin, write, SAVE, drop.
- 3.1·intermediate
  1 step
  PageGuard, pin & two latches
  Tall 8 KB page: BPM lock, pin frame, UPDATE Ava, INSERT Ivy, SAVE.
04 · Replacer
What to evict
When every frame is full, a policy picks a victim. Same students workload — only the rule changes.
4.1·intermediate
1 step
LRU Cache Replacement
Evict the coldest page on the students trace.
Same trace · swap the rule
MRU
LRU-K
Clock
2Q
ARC