Storage control method for database recovery in logless mode

A database management system for managing a database provided in a storage system,

• wherein said storage system comprises a first storage subsystem and a second storage subsystem,
• said first storage subsystem comprises a first DB storage device capable of storing a database, a first log storage device capable of storing a log of said database, and a first storage controller for controlling copying in accordance with the pair state of the respective storage devices;
• and
• said second storage subsystem comprises a second DB storage device capable of being paired with said first DB storage device, a second log storage device capable of being paired with said first log storage device, and a second storage controller capable of communicating with said first storage controller,
• and wherein, said first storage subsystem is constituted such that, when a DB-pair state, which is the pair state of said first DB storage device and said second DB storage device, is a pair-split state, and a difference occurs between said first DB storage device and said second DB storage device, the difference is managed, and when the pair-split state is cancelled, said first storage controller, by sending said managed difference to said second storage controller, can cause said second storage controller to update said difference in said second DB storage device, thereby doing away with the difference between said first DB storage device and said second DB storage device, and
• prior to the start of a transaction, a log-pair state, which is a pair state between said first log storage device and said second log storage device, constitutes a synchronous/asynchronous pair state in which data written to said first log storage device is transferred to said second log storage device either synchronously or asynchronously with a write to a prescribed region of said first storage subsystem, and by so doing, when data is written to said first log storage device, said first storage controller sends the data to said second storage controller, and said second storage controller writes the data to said second log storage device,
• said database management system, when, as a log control mode, which is a mode related to controlling a log of a database, are provided a logless mode, which is a mode in which a log comprising at least database update history is not created even if said database is updated during a transaction, and a mode, which differs from said logless mode, and a transaction is executed in said logless mode, creates at the start of this transaction a logless-start log, which is a log denoting the start of said logless mode, and issues the logless-start log to said first log storage device, thereby writing the logless-start log to said first log storage device;
• and executes DB updating by which a plurality of data are respectively issued to a database of said first DB storage device;
• and issues to said first storage subsystem a pair command for canceling a pair-split state between said first DB storage device and said second DB storage device either prior to the start or subsequent to the completion of said DB updating while a transaction-in-progress is being executed, thereby canceling this pair-split state;
• and when the difference between said first DB storage device and said second DB storage device has been done away with subsequent to the end of said DB updating, creates a logless-end log, which is a log denoting the termination of said logless mode, and issues this logless-end log to said first log storage device, thereby writing this logless-end log to said first log storage device.

A database management method for managing a database provided in a storage system;

• wherein said storage system comprises a first storage subsystem and a second storage subsystem;
• said first storage subsystem comprises a first DB storage device capable of storing a database, a first log storage device capable of storing a log of said database, and a first storage controller for controlling copying in accordance with the pair state of the respective storage devices;
• and
• said second storage subsystem comprises a second DB storage device capable of being paired with said first DB storage device, a second log storage device capable of being paired with said first log storage device, and a second storage controller capable of communicating with said first storage controller,
• and wherein, said first storage subsystem is constituted such that, when a DB-pair state, which is the pair state of said first DB storage device and said second DB storage device, is a pair-split state, and a difference occurs between said first DB storage device and said second DB storage device, the difference is managed, and when the pair-split state is cancelled, said first storage controller, by sending said managed difference to said second storage controller, can cause said second storage controller to update said difference in said second DB storage device, thereby doing away with the difference between said first DB storage device and said second DB storage device, and
• prior to the start of a transaction, a log-pair state, which is a pair state between said first log storage device and said second log storage device, constitutes a synchronous/asynchronous pair state in which data to be written to said first log storage device is transferred to said second log storage device either synchronously or asynchronously with a write to a prescribed region of said first storage subsystem, and by so doing, when data is written to said first log storage device, said first storage controller sends the data to said second storage controller, and said second storage controller writes the data to said second log storage device,
• said database management method comprising the steps of:
• creating, when, as a log control mode, which is a mode related to controlling a log of a database, are provided a logless mode, which is a mode in which a log comprising at least database update history is not created even if said database is updated during a transaction, and a mode, which differs from said logless mode, and a transaction is executed in said logless mode, at the start of the transaction a logless-start log, which is a log denoting the start of said logless mode, and issuing said logless-start log to said first log storage device, thereby writing this logless-start log to said first log storage device;
• executing DB updating by which a plurality of data are respectively issued to a database of said first DB storage device;
• issuing to said first storage subsystem a pair command for canceling a pair-split state between said first DB storage device and said second DB storage device either prior to the start or subsequent to the completion of said DB updating while a transaction-in-progress is being executed, thereby canceling this pair-split state;
• and
• creating a logless-end log, which is a log denoting the termination of said logless mode, and issuing said logless-end log to said first log storage device when the difference between said first DB storage device and said second DB storage device has been done away with subsequent to the end of said DB updating, thereby writing this logless-end log to said first log storage device.

A computer for managing a database provided in a storage system,

• wherein said storage system comprises a first storage subsystem and a second storage subsystem;
• said first storage subsystem comprises a first DB storage device capable of storing a database, a first log storage device capable of storing a log of said database, and a first storage controller for controlling copying in accordance with the pair state of the respective storage devices, and
• said second storage subsystem comprises a second DB storage device capable of being paired with said first DB storage device, a second log storage device capable of being paired with said first log storage device, and a second storage controller capable of communicating with said first storage controller,
• and wherein said first storage subsystem is constituted such that, when a DB-pair state, which is the pair state of said first DB storage device and said second DB storage device, is a pair-split state, and a difference occurs between said first DB storage device and said second DB storage device, the difference is managed, and when the pair-split state is cancelled, said first storage controller, by sending said managed difference to said second storage controller, can cause said second storage controller to update said difference in said second DB storage device, thereby doing away with the difference between said first DB storage device and said second DB storage device, and
• prior to the start of a transaction, a log-pair state, which is a pair state between said first log storage device and said second log storage device, constitutes a synchronous/asynchronous pair state in which data to be written to said first log storage device is transferred to said second log storage device either synchronously or asynchronously with a write to a prescribed region of said first storage subsystem, and by so doing, when data is written to said first log storage device, said first storage controller sends the data to said second storage controller, and said second storage controller writes the data to said second log storage device,
• said computer comprising:
• a logless-start log issuing unit, which, when, as a log control mode, which is a mode related to controlling a log of a database, are provided a logless mode, which is a mode in which a log comprising at least database update history is not created even if said database is updated during a transaction, and a mode, which differs from said logless mode, and a transaction is executed in said logless mode, creates at the start of this transaction a logless-start log, which is a log denoting the start of said logless mode, and issues said logless-start log to said first log storage device;
• a DB operation unit for executing DB updating by which a plurality of data are respectively issued to a database of said first DB storage device;
• a pair command unit for issuing to said first storage subsystem a pair command for canceling a pair-split state between said first DB storage device and said second DB storage device either prior to the start or subsequent to the completion of said DB updating while a transaction-in-progress is being executed;
• and
• a logless-end log issuing unit, which, when the difference between said first DB storage device and said second DB storage device has been done away with subsequent to the end of said DB updating, creates a logless-end log, which is a log denoting the termination of said logless mode, and issues the logless-end log to said first log storage device.

A storage subsystem capable of communicating with an external storage subsystem, the storage subsystem comprising:

• a first DB storage device capable of storing a database;
• a first log storage device capable of storing a log of said database;
• and
• a controller,
• wherein said external storage subsystem comprises a second DB storage device capable of being paired with said first DB storage device, and a second log storage device capable of being paired with said first log storage device;
• and
• said controller is constituted such that, when a DB-pair state, which is the pair state of said first DB storage device and said second DB storage device, is a pair-split state, and a difference occurs between said first DB storage device and said second DB storage device, the difference is managed, and when the pair-split state is cancelled, said first storage controller, by sending said managed difference to said second storage controller, can cause said second storage controller to update said difference in said second DB storage device, thereby doing away with the difference between said first DB storage device and said second DB storage device, and
• prior to the start of a transaction, a log-pair state, which is a pair state between said first log storage device and said second log storage device, constitutes a synchronous/asynchronous pair state in which data to be written to said first log storage device is transferred to said second log storage device either synchronously or asynchronously with a write to a prescribed region of said first storage subsystem, and by so doing, when data is written to said first log storage device, said controller sends the data to said external storage subsystem so that the data is written to said second log storage device,
• said controller, when, as a log control mode, which is a mode related to controlling a log of a database, are provided a logless mode, which is a mode in which a log comprising at least database update history is not created even if said database is updated during a transaction, and a mode, which differs from said logless mode, and a transaction is executed in said logless mode, creates at the start of the transaction a logless-start log, which is a log denoting the start of said logless mode, and writes said logless-start log to said first log storage device;
• and executes DB updating by which a plurality of data are respectively issued to a database of said first DB storage device;
• and cancels a pair-split state between said first DB storage device and said second DB storage device either prior to the start or subsequent to the completion of said DB updating while a transaction-in-progress is being executed;
• and creates a logless-end log, which is a log denoting the termination of said logless mode, and writes the logless-end log to said first log storage device when the difference between said first DB storage device and said second DB storage device has been done away with subsequent to the end of said DB updating.