Oracle 19c Faster Cluster Node Recovery
Oracle 19c Faster Cluster Node Recovery (FCNR)
Introduction
In Oracle RAC environments, node failures are not rare OS crashes, network issues, storage hiccups, or planned maintenance can bring down a cluster node.
The real challenge is not the failure itself, but how fast the cluster recovers and resumes normal operations.
With Oracle 19c, Oracle introduced a major enhancement called Faster Cluster Node Recovery (FCNR), significantly reducing instance recovery time after a node failure especially for large RAC databases.
This feature is a game-changer for mission-critical systems where downtime of even a few minutes is unacceptable.
What Is Cluster Node Recovery?
When a RAC node crashes:
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The instance on that node stops abruptly
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Other surviving nodes detect the failure
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Oracle performs:
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Cluster reconfiguration
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Cache recovery
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Instance recovery
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Workload is redistributed
Before 19c, instance recovery was sequential and slow, especially when:
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Large buffer cache existed
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Many dirty blocks were present
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High redo generation workload
The Problem Before Oracle 19c
Traditional Instance Recovery Flow
Earlier RAC versions (11g / 12c):
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One recovery process (SMON)
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Redo applied serially
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Recovery dependent on:
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Redo size
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Dirty buffer count
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I/O throughput
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Resulting Issues
❌ Long recovery time
❌ Extended application downtime
❌ SLA violations
❌ Poor scalability for large RAC clusters
Oracle 19c Solution: Faster Cluster Node Recovery (FCNR)
What FCNR Does
Oracle 19c introduces parallel and distributed instance recovery using multiple recovery slaves.
Instead of one node doing all the recovery work:
👉 Multiple surviving RAC instances participate in recovery
How FCNR Works (Internal Architecture)
Step-by-Step Recovery Flow
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Node Failure Detected
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CSS detects node eviction or crash
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Redo Ownership Distributed
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Redo threads from failed instance are split
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Assigned to multiple surviving nodes
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Parallel Redo Apply
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Each node runs recovery slaves
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Redo is applied in parallel
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Dirty Block Processing Optimized
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Faster block clean-up
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Reduced cache contention
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Instance Recovery Completes
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Services relocate
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Applications resume faster
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Key FCNR Enhancements in Oracle 19c
1️⃣ Parallel Instance Recovery
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Multiple SMON recovery slaves
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Controlled automatically by Oracle
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No manual tuning required in most cases
2️⃣ Dynamic Workload Distribution
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Redo evenly split across nodes
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Prevents one node from becoming a bottleneck
3️⃣ Reduced Recovery I/O
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Smarter redo filtering
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Avoids unnecessary block reads
4️⃣ Faster Service Relocation
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Services start earlier
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Application reconnect time reduced
Important Parameters (Mostly Automatic)
Oracle 19c enables FCNR by default.
However, DBAs should be aware of related parameters:
Relevant Parameters
| Parameter | Description |
|---|---|
parallel_recovery_enabled |
Enables parallel recovery |
fast_start_parallel_rollback |
Controls rollback speed |
_lm_drm_disable |
Affects cache fusion behavior (hidden) |
recovery_parallelism |
Auto-managed in 19c |
👉 Best Practice:
Do NOT manually tune hidden parameters unless Oracle Support advises.
Observing FCNR in Action
Alert Log Messages
During recovery, you’ll see messages like:
Check Recovery Slaves
Performance Impact & Benchmarks
Oracle Internal Testing Shows:
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⏱️ Recovery time reduced by 2x–5x
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🚀 Faster application availability
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📉 Reduced cluster instability post-crash
Best Use Cases
✅ Large buffer cache
✅ High redo-rate OLTP systems
✅ 3+ node RAC clusters
✅ 24×7 mission-critical apps
FCNR vs Fast-Start Recovery
| Feature | Fast-Start Recovery | FCNR |
|---|---|---|
| Scope | Single instance | RAC cluster |
| Parallelism | Limited | Multi-node |
| Recovery Speed | Moderate | Very fast |
| Availability | Instance-level | Cluster-level |
👉 FCNR builds on Fast-Start Recovery, but scales it across the cluster.
Common DBA Misconceptions
❌ “FCNR needs manual configuration”
✔️ No, it’s automatic in 19c
❌ “Only useful for huge databases”
✔️ Even mid-size RAC benefits
❌ “It replaces RAC cache recovery”
✔️ No, it optimizes it
Troubleshooting FCNR Issues
If Recovery Is Still Slow
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Check interconnect latency
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Verify storage IOPS
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Review redo log sizes
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Check alert logs for recovery errors
RAC Health Checks
Production Best Practices
✅ Use multiple smaller redo logs
✅ Keep interconnect latency low
✅ Monitor GV$ views during recovery
✅ Test node failure in UAT
✅ Keep GI & DB PSU patches up to date
Interview Questions (Real-World)
Q: What is Faster Cluster Node Recovery in Oracle 19c?
👉 It allows parallel instance recovery across surviving RAC nodes, drastically reducing downtime after a node failure.
Q: Is FCNR enabled by default?
👉 Yes, starting from Oracle 19c.
Q: How does FCNR improve recovery time?
👉 By distributing redo recovery workload across multiple nodes instead of a single instance.
Final Thoughts
Oracle 19c Faster Cluster Node Recovery is one of the most important RAC stability enhancements in recent years.
It directly improves:
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High availability
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SLA compliance
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Application resilience
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DBA peace of mind 😄
If you’re running RAC on 19c and not aware of FCNR you’re already using it, and it’s quietly saving you during node crashes.
With Learnomate Technologies, Oracle DBA training goes beyond theory covering advanced RAC features such as Faster Cluster Node Recovery in Oracle 19c, exactly the way they occur in real-world systems.
Happy learning!
Ankush😎
