Disaster recovery processing method and apparatus and storage unit for the same

Abstract

A technique capable of constructing a disaster recovery system reduced in performance degradation of a primary system is provided. The technique includes a step of conducting synchronous writing of log information into a secondary storage subsystem in a secondary system when a write request received from a host computer is a write request of log information, a step of temporarily storing a write request and conducting asynchronous writing into the secondary storage subsystem when the received write request is a write request of database data or status information, a step of modifying log information, data in a database area, and status information in the secondary storage subsystem according to contents of a write request received from a primary storage subsystem, and a step of recovering the database area according to contents of log information in a location indicated by the status information.

1 . A computer system, which is a primary system to a secondary computer system comprising a secondary host computer and a secondary storage subsystem, the computer system comprising:
 a primary host computer executing a primary database management system program corresponding to a secondary database management system program to be executed by the secondary host computer; and   a primary storage subsystem coupled to the primary host computer and the secondary storage subsystem,   wherein the primary storage subsystem, in response to a write request from the primary host computer, stores primary log information, primary database data, and primary status information, which are modified by the primary host computer based on the execution of the primary database management system program, the primary status information indicating a location of log information to be used at a time of switching transaction processing from the primary host computer to the secondary host computer,   wherein, to the secondary storage subsystem, the primary storage subsystem executes a synchronous remote copy of the primary log information and an asynchronous remote copy of the primary database data and the primary status information, the secondary database management system program causing the secondary host computer to:
 (A) read a copy of the primary status information stored in the secondary storage subsystem, created by the asynchronous remote copy; 
 (B) based on the copy of the primary status information, decide locations on a copy of the primary log information created by the synchronous remote copy, to be used to modify a copy of the secondary database data created by the asynchronous remote copy; 
 (C) read a part of the copy of the primary log information indicated by the locations on the copy of the primary log information; and 
 (D) modify the copy of the primary database data according to the part of the secondary log information so that modification of a completed transaction processed by the primary host computer is stored in the copy of the primary database data. 
   
     
     
         2 . A computer system according to  claim 1 ,
 wherein, as to the modification by the primary host computer, the primary database management system program causes the primary host computer to:   (i) modify the primary database data in the primary storage subsystem based on modification data temporarily buffered in the primary host computer;   (ii) store a checkpoint acquisition log to the primary log information in the primary storage subsystem; and   (iii) modify the primary status information in the primary storage subsystem after the processing of (i) and (ii).   
     
     
         3 . A computer system according to  claim 2 ,
 wherein the primary storage subsystem includes a first primary disk, a second primary disk, and a third primary disk,   wherein the primary log information is stored in the first primary disk,   wherein the primary database data is stored in the second primary disk, and   wherein the primary status information is stored in the third primary disk.   
     
     
         4 . A computer system according to  claim 3 ,
 wherein the step (D) comprises a roll-forward processing and a roll-back processing.   
     
     
         5 . A computer system according to  claim 4 ,
 wherein the secondary database management system program causes the secondary host computer to:   (E) change an operation state from another state after completion of the roll-forward processing and the roll-back processing.   
     
     
         6 . A disaster recovery method for a computer system being a primary system to a secondary computer system including a secondary host computer and a secondary storage subsystem, the computer system including a primary host computer and a primary storage subsystem, the method comprising:
 by the primary host computer, executing a primary database management system program corresponding to a secondary database management system program to be executed by the secondary host computer;   by the primary storage subsystem, in response to a write request from a primary host computer, storing primary log information, primary database data, and primary status information, which are modified by the primary host computer based on the execution of the primary database management system program, the primary status information indicating a location of log information to be used at a time of switching transaction processing from the primary host computer to the secondary host computer; and   by the primary storage subsystem, executing a synchronous remote copy about the primary log information and an asynchronous remote copy about the primary database data and the primary status information, the secondary database management system program causing the secondary host computer to:
 (A) read a copy of the primary status information stored in the secondary storage subsystem, created by the asynchronous remote copy; 
 (B) based on the copy of the primary status information, decide locations on a copy of the primary log information created by the synchronous remote copy, to be used to modify a copy of the secondary database data created by the asynchronous remote copy; 
 (C) read a part of the copy of the primary log information indicated by the locations on the copy of the primary log information; and 
 (D) modify the copy of the primary database data according to the part of the secondary log information so that modification of a completed transaction processed by the primary host computer is stored in the copy of the primary database data. 
   
     
     
         7 . A disaster recovery method according to  claim 6 ,
 wherein, as to the modification by the primary host computer, the primary database management system program causes the primary host computer to:   (i) modify the primary database data in the primary storage subsystem based on modification data temporarily buffered in the primary host computer;   (ii) store a checkpoint acquisition log to the primary log information in the primary storage subsystem; and   (iii) modify the primary status information in the primary storage subsystem after the processing of (i) and (ii).   
     
     
         8 . A disaster recovery method according to  claim 7 ,
 wherein the step (D) comprises a roll-forward processing and a roll-back processing.   
     
     
         9 . A disaster recovery method according to  claim 8 ,
 wherein the secondary database management system program causes the secondary host computer to:   (E) change an operation state from another state after completion of the roll-forward processing and the roll-back processing.