Data transfers between cluster instances with delayed log file flush

摘要

Techniques for processing changes in a cluster database system are provided. A first instance in the cluster transfers a data block to a second instance in the cluster before a redo record that stores one or more changes that the first instance made to the data block is durably stored. The first instance also transfers, to the second instance, a block change timestamp that indicates when a redo record for the one or more changes was generated by the first instance. The first instance also separately sends, to the second instance, a last store timestamp that indicates when the last redo record that was durably stored was generated by the first instance. The block change timestamp and the last store timestamp are used by the second instance when creating redo records for changes (made by the second instance) that depend on the redo record generated by the first instance.

主权项

1. A method comprising:
receiving, at a first node in a cluster of nodes of a database system, from a second node in the cluster of nodes, a request for first data that the first node has modified; wherein each node in the cluster of nodes executes one or more database server instances; prior to the first node durably storing redo data that indicates one or more changes that have been made to the first data, sending, from the first node, to the second node in the cluster of nodes, the first data that includes the one or more changes; wherein sending the first data comprises sending timestamp data that indicates when the redo data was generated at the first node; wherein sending the timestamp data to the second node comprises sending, to the second node, a plurality of timestamp values; wherein each timestamp value of the plurality of timestamp values indicates when certain redo data, upon which the first data depends, was generated by a different respective instance of a plurality of instances in the cluster of nodes; wherein the method is performed by one or more computing devices.