Database Failback Using Snapshot and Transaction Log Replication

Solution Overview

Problem

Current database systems face challenges in efficiently restoring operation after failure, particularly in maintaining data consistency and minimizing downtime during failback operations, as they often require a full data copy from the secondary database system, which can be time-consuming and resource-intensive.

Innovation Solution

The implementation of a failback operation using a snapshot and logical equivalent replication, where the first database system registers with the second database system, opens a snapshot of shared data, requests and applies transaction log information from the second database system, and updates its data to match the second database system's state, allowing for faster restoration without requiring a full data copy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a full data copy is performed from the secondary database system during failback, then data consistency is ensured, but restoration time and resource consumption increase significantly

Engineering Contradiction:

Improvedata consistencyVSAvoidrestoration time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent applies preliminary action by creating and storing snapshots of the primary database system at predetermined intervals before failure occurs. These snapshots are pre-prepared and stored in persistent storage, so when failback is needed, the system can quickly restore from the most recent snapshot without performing a complete data copy, thus reducing restoration time while maintaining data consistency through the use of transaction logs to catch up any differences.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If a full data copy is performed from the secondary database system during failback, then data consistency is ensured, but resource consumption increases significantly

Engineering Contradiction:

Improvedata consistencyVSAvoidresource consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent applies preliminary action by creating and storing snapshots of the primary database system at predetermined intervals before failure occurs. These snapshots are pre-prepared and stored in persistent storage, so when failback is needed, the system can quickly restore from the most recent snapshot without performing a complete data copy, thus reducing restoration time while maintaining data consistency through the use of transaction logs to catch up any differences.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies the copying principle by using snapshots - which are lightweight copies of the database state at a specific point in time - instead of performing full data copies during failback. The snapshot contains only the necessary data structures and metadata to reconstruct the database state, significantly reducing the resources required compared to copying entire datasets, while still ensuring data consistency through subsequent transaction log application.

Inventive Principle:

Principle #26Copying

3Productivity

If the second database system is used as the primary system after failure, then system availability is maintained, but data loss may occur for transactions that occurred after the failover

Engineering Contradiction:

Improvesystem availabilityVSAvoiddata loss

Core Design Contradiction:

ProductivityVSLoss of information

Solution Approach 1:

The patent applies beforehand cushioning by maintaining snapshots of the primary database system at predetermined intervals before failure. These snapshots serve as a safety cushion or backup state that can be restored if needed. When failback is performed, the system can recover to a known good state from the snapshot and then replay transaction logs to minimize data loss, providing a cushion against potential data loss scenarios while maintaining high system availability.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS10769040B2Logical equivalent replication with snapshot based fallback of database systems

Publication Date: 2020.09.08 SAP SE

AI summary

A computer implemented method for replication includes registering a first database system with a second database system and performing a failback operation on the first database system. The failback operation includes opening a snapshot that includes data known to have existed on the first database system and the second database system at a first time. Transaction log information is requested from the second database system. The transaction log information corresponds to transactions performed on the second database system beginning with the first time. The transaction log information is applied to the snapshot data on the first database system. Related apparatus, systems, techniques and articles are also described.