1. Each file is partitioned into fixed-length storage units, called blocks, which are the units of both storage allocation and data transfer.

2. It is desirable to keep as many blocks as possible in main memory. Usually, we cannot keep all blocks in main memory, so we need to manage the allocation of available main memory space.

3. We need to use disk storage for the database, and to transfer blocks of data between main memory and disk.We also want to minimize the number of such transfers, as they are time-consuming.

4. The buffer is the part of main memory available for storage of copies of disk blocks.