Oracle RAC Dynamic Service Fallback Usage

1Z0-078 By islever Editorial Last updated

Services, load balancing and connection management

Short answer

D Dynamic Service Fallback allows a service to fall back to a preferred instance when it becomes available after it was failed over to an available instance.

Question

Which statement describes the usage of Dynamic Service Fallback in Oracle RAC 19c?
  1. Dynamic Service Fallback allows a service to relocate to an available instance when the service is stopped on a preferred instance.
  2. Dynamic Service Fallback allows a service to fall back to a preferred instance when the available instance performance falls below a specified threshold after it was failed over to an available instance.
  3. To enable Dynamic Service Fallback, you should specify the level of performance of a preferred instance for a service to be relocated to an available instance by setting the -failback attribute of a service to "Low, Medium, or High".
  4. Dynamic Service Fallback allows a service to fall back to a preferred instance when it becomes available after it was failed over to an available instance. Correct Answer

Key Takeaways

The exam tests the specific condition that triggers Dynamic Service Fallback: distinguishing between 'availability' and 'performance metrics'. The common trap is confusing fallback with load balancing or performance-based relocation.

Dynamic Service Fallback in Oracle RAC 19c automatically moves a service back to its preferred instance once it becomes available after a failover. This question establishes that the trigger for fallback is instance availability, not performance thresholds.

Common mistake: Option B is the most likely distractor because it introduces performance thresholds, which are part of Load Balancing Goal (LBGOAL) but not the primary definition of Service Fallback behavior itself.

Expert Analysis

Why the Answer Is Correct

Dynamic Service Fallback is designed to restore services to their 'preferred' instances as soon as those instances become available again after a failure or planned maintenance. When a service fails over to an available instance due to a preferred instance being down, the fallback mechanism monitors the preferred instance's status. Once the preferred instance recovers and becomes available, the service is moved back to it. This ensures optimal resource utilization based on administrative preferences.

Why the Other Options Are Wrong

Option A describes a relocation triggered by stopping the service, which is not the definition of automatic fallback. Option B incorrectly attributes fallback to performance thresholds; while performance goals exist, the fundamental trigger for 'fallback' in this context is the return of availability. Option C is technically incorrect regarding the -failback attribute configuration syntax and logic; failback is generally automatic upon availability recovery, not strictly tied to Low/Medium/High performance levels in the way described.

Community Comment Notes

Community consensus strongly supports Option D, with users citing official Oracle documentation confirming that fallback occurs when the preferred instance becomes available. Comments highlight that this behavior is distinct from performance-driven load balancing, reinforcing that availability is the key trigger.

Official Reference

https://docs.oracle.com/en/database/oracle/oracle-database/19/racad/changes-in-this-release-for-oracle-real-application-clusters-administration-and-deployment-guide.html

This link opens the official vendor documentation in a new tab.

Exam Strategy

Always distinguish between 'Load Balancing' (which often involves performance goals and distribution) and 'Failover/Fallback' (which involves availability and instance preference). For fallback questions, look for keywords like 'becomes available' rather than 'performance falls below'.

Frequently Asked Questions

Does Dynamic Service Fallback depend on performance metrics?

No, it primarily depends on the availability of the preferred instance. Performance metrics are handled by Load Balancing Goals.

What triggers a service to move back to a preferred instance?

The trigger is the preferred instance becoming available again after a failure or downtime event.

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Community Votes

D
100%

100% of anonymous learners picked answer D. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 3 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 3

  1. 217972f 👍 1
    It's D: https://docs.oracle.com/en/database/oracle/oracle-database/19/racad/changes-in-this-release-for-oracle-real-application-clusters-administration-and-deployment-guide.html
  2. 217972f 👍 2 Answered D
    Sure of D
  3. wiprooracle 👍 1
    Looks to be D

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