Shadow Address Space Swapping for Continuous Job Availability

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Solution Overview

Problem

In some operating systems, when a fix or enhancement is applied to a running job, the job needs to be restarted, which requires reallocating its address space, making it unavailable during the restart period. This poses challenges for services like disaster recovery and continuous availability of storage devices.

Innovation Solution

The method involves initializing a shadow address space for an active address space, receiving a request to swap, copying state information from the active to the shadow address space, and swapping usage from the active to the shadow address space, allowing the job to use the shadow address space without downtime.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a job is restarted to apply fixes or enhancements, then the job can operate with updated software, but the address space becomes unavailable during the restart period causing downtime

Engineering Contradiction:

Improvecontinuous availabilityVSAvoiddowntime during restart

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

A shadow address space is initialized and kept ready in advance before any restart is needed. This shadow address space is pre-configured and can be swapped into use immediately when a restart is required, eliminating the downtime that would otherwise occur during address space reallocation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The shadow address space is created as a copy of the active address space structure. State information can be copied from the active address space to the shadow address space, allowing the shadow space to be prepared in advance with all necessary components ready for immediate swapping when needed.

Inventive Principle:

Principle #26Copying

2Adaptability or versatility

If the address space is reallocated during job restart, then fixes and enhancements can be applied, but the service becomes unavailable during the restart period

Engineering Contradiction:

Improveability to apply fixesVSAvoidservice availability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The shadow address space is prepared in advance with all necessary structures and configurations. When a fix or enhancement needs to be applied, the system can swap to the pre-prepared shadow address space immediately, maintaining service availability while the active address space is updated.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The shadow address space acts as an intermediary that allows the active address space to be updated without affecting service continuity. The shadow space serves as a buffer that maintains service availability while the active space undergoes updates.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Loss of time

If state information is copied from active to shadow address space, then seamless swapping is enabled, but additional memory operations are required

Engineering Contradiction:

Improveswapping downtimeVSAvoidmemory operation overhead

Core Design Contradiction:

Loss of timeVSUse of energy by moving object

Solution Approach 1:

State information is copied to the shadow address space in advance, before swapping is needed. This preliminary copying eliminates the need for time-critical memory operations during the actual swap, reducing downtime even though it requires additional memory operations beforehand.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS20250190255A1Swapping from an active address space to a shadow address space

Publication Date: 2025.06.12 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

Swapping from an active address space to a shadow address space may include: initializing, for an active address space, a shadow address space; receiving a request to swap from the active address space to the shadow address space; in response to the request, copying state information from the active address space to the shadow address space; and swap usage of the active address space to the shadow address space.