Method and apparatus for managing a buffer pool referenced by batch and interactive process

Claim 1

A method for operating a computing apparatus including a main processor (10), a plurality of main storage buffers (14), and at least one external storage device (30); the main processor being operated under control of a data base system which includes a buffer manager (20) for allocating data set pages read from the storage device into the buffers for concurrent access by both sequential and random processes; the method being characterized by the steps of: (1) establishing a queue value; (2) maintaining a normal least recently used (LRU) buffer chain (34) and a sequential LRU buffer chain (36) with the sequential LRU buffer chain replicated on the normal LRU buffer chain; (3) placing buffers (14) released from a sequential process (16) that is not a prefetch process in both LRU buffer chains, and placing buffers released from a random process (18) or from a sequential prefetch process only in the normal LRU buffer chain; and (4) responsive to a request for a buffer from a sequential process (16), stealing the head buffer from the sequential LRU buffer chain (36) provided the number of buffers in that chain exceeds the queue value, otherwise stealing the head buffer from the normal LRU chain (34), thereby preventing recursive steals of buffers employed in nested sequential processes.

Claim 2

A method for operating a computing apparatus including a main processor (10), a plurality of main storage buffers (14), and at least one external storage device (30); the main processor being operated under control of a data base system which includes a buffer manager (20) for allocating data set pages read from the storage device into the buffers for concurrent access by both sequential and random processes; the method being characterized by the steps of: (1) establishing a queue value; (2) maintaining a normal least recently used (LRU) buffer chain (34) and a sequential LRU buffer chain (36) with the sequential LRU buffer chain replicated on the normal LRU buffer chain; (3) placing buffers (14) released from a sequential process (16) that is not a prefetch process in both LRU buffer chains, and placing buffers released from a random process (18) or from a sequential prefetch process only in the normal LRU buffer chain; and (4) responsive to a request for a buffer from a sequential process (16), stealing the head buffer from the sequential LRU buffer chain (36) provided the number of buffers in that chain exceeds the queue value, otherwise stealing the head buffer from the normal LRU chain (34), thereby preventing recursive steals of buffers employed in nested sequential processes.

Claim 4

The method of claims 1 and 2 for preventing monopolization of a buffer pool by sequential processes sharing the buffer pool concurrently with random processes.