Disaster recovery method, disaster recovery system, remote copy method and storage system

A disaster recovery method for copying data of a database management system in a main site to a sub-site located in a remote site,

• wherein said method includes a log application process in which logs are transferred through a remote copy operation of a main storage of said main site, and the transferred logs are applied to recover a database of a sub-storage in said sub-site, and
• when the logs are written in units of a log block consisting of a plurality of log records in said main site and the logs are applied in said sub-site, said log application process comprises the steps of:
• reading a log block from said sub-storage to verify consistency;
• determining whether the reading process does not conflict with the writing process through a remote copy operation in the log blocks except for the last one among said read log blocks;
• and
• rereading the log blocks except for the last one and then applying them.

A disaster recovery method for copying data of a database management system in a main site to a sub-site located in a remote site,

• wherein said method includes a log application process in which logs are transferred through a remote copy operation of a main storage of said main site, and the transferred logs are applied to recover a database of a sub-storage in said sub-site,
• when the logs are written in units of a log block consisting of a plurality of log records in said main site and the logs are applied in said sub-site,
• said sub-storage has a first volume and a second volume for one transfer source volume of said main storage,
• the log written to said main storage is additionally written to said first volume of said sub-storage in the order of update through a first copy operation representing a remote copy operation, and a copy to said second volume is reflected through a second copy operation at the timing different from the writing to said first volume,
• said log application process in said sub-site comprises the steps of:
• interrupting said second copy operation;
• reading the log block from said second volume;
• applying said read log block;
• and
• restarting said second copy operation after interrupting said log application process when there is not any log to be read, and
• the logs are applied in said sub-site independently to recover the database.

A disaster recovery system for copying data of a database management system in a main site to a sub-site located in a remote site,

• wherein said main site includes a first computer on which the database management system is operated and a first storage to record a database and logs as the history of updating said database,
• said sub-site includes a program to execute a log application process, a second computer on which said program is operated and a second storage to record a database and logs,
• said main site and said sub-site are connected through a network,
• said first and second storages have a remote copy function, the log recorded in said first storage is copied to said second storage by the remote copy function,
• the database management system of said main site writes the logs in units of a log block consisting of a plurality of log records,
• the log application process of said sub-site includes the steps of:
• reading log blocks;
• determining whether the reading process does not conflict with the writing process through the remote copy operation in the log blocks except for the last one among the read log blocks;
• and
• rereading the log blocks except for the last log block and applying them, and
• the logs are applied in said sub-site independently to recover the database.

A disaster recovery system for copying data of a database management system in a main site to a sub-site located in a remote site,

• wherein said main site includes a first computer on which the database management system is operated and a first storage to record a database and logs as the history of updating said database,
• said sub-site includes a program to execute a log application process, a second computer on which said program is operated and a second storage to record a database and logs,
• said main site and said sub-site are connected through a network,
• said first and second storages have a remote copy function, the log recorded in said first storage is transferred to said second storage by the remote copy function,
• said second storage to which the logs are transferred has first and second volumes for one transfer source volume of said first storage, the log transferred from said first storage is additionally written to said first volume, and a second copy operation from said first volume to said second volume is performed at the timing different from a remote copy operation which is a first copy operation,
• in the log application process in said sub-site, logs are read from said second volume, said second copy operation is interrupted before reading and applying the logs, and then, said second copy operation is restarted after the read log is completely applied, and
• the logs are applied in said sub-site independently to recover the database.