Asynchronous remote mirroring techniques for databases

摘要

There is provided a method and system to asynchronously remotely copy database content changes from a primary site to a remote site utilizing consistency groups. Log information and data are separated. When log information and data are copied to the remote site, the log information is given priority over data. Data is not copied for the current consistency group for which log information is in the process of being copied, until all log information in the current consistency group has been copied. Thus, only data included as part of the consistency groups for which all log information has been copied, is copied to the remote site. Because most logs are written sequentially, copying the log blocks immediately does not result in a larger amount of data being copied. In addition, since the log block has been copied over at the earliest instant possible, the extent of data loss has been reduced to the minimum possible in an asynchronous system.