TIME-BASED CHECKPOINT TARGET FOR DATABASE MEDIA RECOVERY

摘要

A method, apparatus, and system for a time-based checkpoint target is provided for standby databases. Change records received from a primary database are applied for a standby database, creating dirty buffer queues. As the change records are applied, a mapping is maintained, which maps timestamps to logical times of change records that were most recently applied at the timestamp for the standby database. On a periodic dirty buffer queue processing interval, the mapping is used to determine a target logical time that is mapped to a target timestamp that is prior to a present timestamp by at least a checkpoint delay. The dirty buffer queues are then processed up to the target logical time, creating an incremental checkpoint. On a periodic header update interval, file headers reflecting a consistent logical time for the checkpoint are also updated. The intervals and the checkpoint delay are adjustable by user or application.

主权项

1. A method comprising:
applying, for a standby database, a plurality of change records received from a primary database, the applying creating one or more queues of dirty buffers, each dirty buffer having a logical time of a change record that was applied into said dirty buffer; maintaining a mapping for a plurality of timestamps, wherein each timestamp of said plurality of timestamps is mapped to a logical time of a particular change record of said plurality of change records, said particular change record being a latest applied change record for the standby database as of said each timestamp; using the mapping, determining a target logical time mapped to a target timestamp that is prior to a present timestamp by at least a checkpoint delay; creating a checkpoint describing one or more database files of the standby database at a consistent logical time, wherein the creating writes a set of dirty buffers, from the one or more queues of dirty buffers, that have logical times up to the target logical time; wherein the method is performed by one or more computing devices.