Sequentially processing data in a cached data storage system

DETAILED DESCRIPTION Referring now more particularly to the appended drawings, like numerals indicate like features in the various figures.
Referring more particularly to FIG.
1, the environment in which the invention is practiced is described.
One or more host processors are connected to the illustrated data storage subsystem via an attachment or channel 10.
The data storage subsystem includes one or more data storage devices 11, preferably disk recorders also referred to as direct access storage devices (DASD).
A programmed control 12 in the peripheral data storage subsystem controls the subsystem operations and the transfer of data between DASD 11 and host processors through attachment 10.
Line 13 indicates this control function, which is well known.
Programmed control 12 has its own microprocessor (not shown), such as seen in U.
S.
Pat.
No.
4,466,059.
Particularly refer to FIG.
2 of the cited patent which shows the hardware arrangement which may be advantageously employed with the present invention.
Programmed control 12 has its own control program storage which includes a set of control programs (pgms) 14.
The microprocessor in programmed control 12 reads the control programs and responds thereto for effecting control and management of the data storage subsystem as represented by line 13.
The operation and management also requires a set of control tables 15 which store control commands and other parameters received from the host processors, status information about the data storage subsystem, as well as other parameters useful for operating a data storage subsystem, all as is known.
To enhance the performance of the data storage subsystem, a cache 17 is logically and electrically interposed between DASD 11 and the attachment 10.
Operation of a cache 17 is also described in the documents incorporated by reference.
Programmed control 12 has additional control programs named sequential programs (seq pgms) 24 for managing the cache as well as controlling the DASD 11 in accordance with the present invention