Buffer

A buffer is the potrtion of the main memory designated to store copies of disk blocks. This reduces the number of average calls sent to the disk to fetch data.

Buffer Manager

This is the subsystem that demarcates the buffer space in the main memory. * when a block is needed from the disk, a request is sent to the buffer manager * the buffer manager behaves as a cache, and returns an address from within the buffer

Rearrangement

The OS or buffer manager can reorder writes to keep consistency in check, depending upon how the data structure is stored

Pinned Block

A pinned block cannot be written back to the disk. A block is pinned when work is started on the block, and unpinned when this work is done. This helps in maintaining concurrency.

Buffer Locks

A reader gets a shared lock, while a writer gets an exclusive lock. This means that many readers can read simultaneously, but no writer can write as long as even one reader is reading. When a writer is writing, no one can read.