Outside of the normal cache manager, the server provides additional buffer management techniques specific to read-only data. These techniques are available when the user isolation level is set to dirty read (DR), snapshot read (SR) or exclusive use (EU).
In this cases, the server provides buffered I/O at the cursor level.
If sequential access of a database object is detected within an individual cursor, sequential prefetch of data can be triggered, allowing multiple data pages to be read into a buffer controlled by that individual cursor. This method of buffer management enjoys the benefits of reduced I/O without the normal cache manager overhead (search and toss), and eliminates the need for critical sections.