Dual Vary Off Mechanism for Mirrored Database Nodes

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Solution Overview

Problem

In mirroring environments, the 'block one and track the other' approach for managing databases across a pair of system nodes is vulnerable to data loss and synchronization issues during resynchronization, leading to potential failures and prolonged downtime, especially when switching databases between locations or during disaster recovery.

Innovation Solution

Implementing a dual vary off operation, where both nodes in a mirroring environment are taken offline simultaneously and brought back online in sync, ensuring complete synchronization and reducing the need for resynchronization, thereby maintaining data integrity and minimizing downtime.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the 'block one and track the other' approach is used to manage databases across mirrored nodes, then one node can remain available for updates while the other is taken offline, but this creates synchronization inconsistencies and potential data loss during resynchronization

Engineering Contradiction:

Improveavailability for updatesVSAvoiddata synchronization

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent applies preliminary action by flushing all changed pages from main storage to disk storage before bringing the blocked node back online. This ensures that all updates are safely persisted and synchronized before the node re-enters service, preventing data loss while maintaining availability.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary resynchronization process that mediates between the tracked node and blocked node. The tracked node acts as an intermediary source, providing updates to the blocked node during resynchronization, ensuring data consistency while both nodes are brought back online.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If resynchronization is performed by bringing back online the tracked node first, then the blocked node, then data consistency can be maintained, but this increases management overhead and downtime

Engineering Contradiction:

Improvedata consistencyVSAvoiddowntime

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent performs preliminary actions by flushing all changed pages to disk before bringing the blocked node online. This pre-synchronization reduces the resynchronization workload and time required, as the blocked node already has most updates persisted when it re-enters service.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent enables continuous availability by allowing the tracked node to remain online and accepting updates throughout the resynchronization process. The useful action of processing transactions continues uninterrupted on the tracked node while the blocked node is being restored.

Inventive Principle:

Principle #20Continuity of useful action

3Ease of operation

If the blocked node is brought back online first without resynchronization, then availability is improved, but data loss occurs because updates may be sent out of order

Engineering Contradiction:

ImproveavailabilityVSAvoiddata loss

Core Design Contradiction:

Ease of operationVSLoss of information

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

4Adaptability or versatility

If seamless switching between mirrored nodes is required for disaster recovery or maintenance, then operational continuity is improved, but the traditional approach requires prolonged downtime during resynchronization

Engineering Contradiction:

Improveseamless switching capabilityVSAvoiddowntime

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The patent performs preliminary flushing of all changed pages to disk before node switching or maintenance activities. This pre-synchronization ensures that when a node is brought back online after maintenance or during disaster recovery, minimal resynchronization is needed, enabling seamless switching with minimal downtime.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent maintains continuous operational capability by allowing the other mirrored node to remain online and accept updates during the entire process. This continuity of useful action ensures that business operations continue uninterrupted while maintenance or disaster recovery activities are performed.

Inventive Principle:

Principle #20Continuity of useful action

Data Source

PatentUS11269923B2Ability to vary on and vary off databases simultaneously across two systems

Publication Date: 2022.03.08 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

Embodiments of the present disclosure provide techniques to vary on and vary off databases simultaneously across a pair of nodes in a mirroring environment. A dual vary off operation is initiated at a first node of the pair of nodes, the dual vary off operation to be performed on copies of a database respectively stored on the pair of nodes, the operation to be performed in tandem with the second node. At the first node the copy of the database stored on the first node is informed of the dual vary off operation, and an operating system of the first node is also informed of the dual vary off operation. Upon receipt at the first node of an indication from the second node that it has completed its vary off operation, the first node completes the dual vary off operation. An analogous technique is performed for a dual vary on operation.