Policy-Managed RAC Singleton Service Failover
Short answer
CE The AR singleton service in prod_pool can fail over only to another CDB1 instance within prod_pool and runs on exactly one such instance at any time.
Question
Key Takeaways
This question tests singleton service behavior in policy-managed RAC and the trap of assuming all CDB1 instances belong to prod_pool.
In a six-instance policy-managed RAC database, the AR service is created in server pool prod_pool with cardinality 3, making it a singleton service. This page establishes that AR can fail over only to another instance within prod_pool and runs on exactly one instance at a time, so the correct statements are C and E.
Common mistake: Many learners choose A, believing AR can fail over to any of the six CDB1 instances, but the server pool contains only three of them, so singleton failover is limited to prod_pool.
Expert Analysis
Why the Answer Is Correct
The AR service is a singleton service in the policy-managed server pool prod_pool (cardinality 3). A singleton service runs on exactly one instance in its server pool at any given time, so statement E is true. If that instance fails, Oracle Clusterware can relocate the service to another available instance within prod_pool; since CDB1 has six instances but only three are in prod_pool, the failover target must be one of those three. Thus statement C is also true. A singleton service does not run on multiple instances simultaneously, so B is false.
Why the Other Options Are Wrong
Statement A is false because CDB1 is a six-instance database, yet prod_pool has cardinality 3, meaning only three instances are members of the pool. A failover target must be in the same server pool, so AR cannot fail over to any of the six CDB1 instances. Statement B is false because a singleton service is not available on every instance in the pool; it runs on one instance. Statement D is false because AR is not tied to HOST01; it can be relocated to another instance in prod_pool if the current instance fails or is stopped. The commands executed on HOST01 create the service but do not pin it permanently to that host.
Community Comment Notes
As Jaroslav113 noted, "all the instances are not in the prod_pool" — only three of the six CDB1 instances are there, which invalidates option A. jackhsu0704 also identified the service as a singleton and selected C and E, matching the service's one-instance-at-a-time behavior. krwi1 voted AC by assuming every CDB1 instance runs in prod_pool, but that contradicts the six-instance count versus cardinality of three. The AC vote majority likely stems from this same misconception, while the CE reasoning aligns with Oracle's policy-managed service model.
Official Reference
https://docs.oracle.com/en/database/oracle/oracle-database/19/racad/srvctl-add-service.html
This link opens the official vendor documentation in a new tab.
Exam Strategy
In policy-managed RAC questions, always check the server pool cardinality versus the total number of database instances. Then determine the service cardinality (SINGLETON vs UNIFORM); a singleton is confined to its pool and runs on one instance at a time.
Frequently Asked Questions
Why can AR not fail over to any available CDB1 instance?
What does singleton mean for the AR service in prod_pool?
Community Votes
67% of anonymous learners picked answer AC. Votes are pick records left by other test-takers — they are not the verified answer.
Discussion 5 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 5
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Jaroslav113 👍 4CE ; E...one (any) instance from the pool in one time. A...all the instances are not in the prod_pool ( just 3 of them)
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krwi1 👍 2A - true - AR can fail over to any instance (all the instances are in prod_pool) B - false - AR is singleton service - it can run only on one instance C - true (all the CDB1 instances run in the prod_pool) D - false - we do not know if cdb1 instance is running on host01 now E - false - AR is singleton service - it can run only on one instance at the time
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jackhsu0704 👍 2singleton ==> So C. AR can fail over to any other available CDB1 instance in prod_pool. E. AR is available on any one available CDB1 instance in prod_pool at any one time.
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jackhsu0704 👍 2C. AR can fail over to any other available CDB1 instance in prod_pool. E. AR is available on any one available CDB1 instance in prod_pool at any one time.
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217972f 👍 1C: Server pool isolate members of cluster, so service can failover only on member of server pool. D: AR is a new service and srvctl start executed on host1 starts service on that host. Service is running only on host1 because of cardinality.
Reader comments & corrections
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