Primary Examiner—Robert W. Beausoliel, Jr.
Assistant Examiner—Phung Chung
Attorney, Agent, or Firm—F. E. Anderson; D. A. Shifrin; H.
Primary and secondary data processing systems are coupled via a communication system. Data storage in both systems is provided by a log structured array (LSA) system that stores data in compressed form. Each time data are updated within LSA, the updated data are stored in a data storage location different from the original data. Selected data recorded in a primary data storage of the primary system is remote dual copied to the secondary system for congruent storage in a secondary data storage, such as for disaster recovery purposes. The primary systems creates a remote copying session. Within such remote copying session, a series of "pending write update" sessions are ESTABLISHED. All data updated within each pending write update session is a consistency group of data. Within each pending write update session update data are retentively stored in both the primary and secondary systems (such as in a non-volatile cache). Addressability of such update data within a pending write update session is through separate pending write directories. The main (primary and secondary) directory for data is not updated such that all original (not updated) data are addressable. A COMMIT command terminates each pending write update session. Congruence of the sequence of updating in the primary system is maintained in the secondary system updating procedure.
28 Claims, 12 Drawing Sheets
SECONDARY DATA STORAGE OPERATIONS
DURING DATA UPDATE
[ii] Patent Number: 5,555,371
 Date of Patent: Sep. 10, 1996
 DATA BACKUP COPYING WITH DELAYED
DBRECTORY UPDATING AND REDUCED
NUMBERS OF DASD ACCESSES AT A BACK
UP SITE USING A LOG STRUCTURED
ARRAY DATA STORAGE
 Inventors: Linda Marie Duyanovich, Saratoga,
Calif.; William Frank Micka, Tucson,
Ariz.; Robert Wesley Shomler, Morgan
 Assignee: International Business Machines
Corporation, Armonk, N.Y.
 Appl. No.: 276,379
 Filed: Jul. 18,1994
Related U.S. Application Data
 Continuation-in-part of Ser. No. 36,017, Mar. 23, 1993, Pat. No. 5,446,871, and Ser. No. 992,219, Dec. 17, 1992.
 Int. CI.6 G06F 11/34
 U.S. CI 395/182.11
 Field of Search 395/575, 425,
395/182.11, 489; 371/40.1, 61, 62, 2.1,
 References Cited
U.S. PATENT DOCUMENTS 5,214,670 8/1993 Eastridge et al 395/575