Introduction
Many OCI users are noticing sudden cost increases even though their compute or storage usage hasn’t changed. In most cases, this happens because logging features like Flow Logs, DNS Logs, and Load Balancer Logs generate large amounts of data when they are enabled across busy environments. If these logs are turned on for troubleshooting and not disabled later, or if retention and sampling rates are set too high, the log volume grows quickly and leads to unexpected billing spikes. Anyone using OCI can face this situation, especially in production workloads where traffic is high and logging is misconfigured. In the next section, we will look at simple ways to reduce these logging-related costs and the best practices to avoid this issue.
What’s Causing the Cost Spike?
OCI collects logs at multiple layers:
- VCN Flow Logs capturing every network session.
- DNS Logs recording every lookup.
- Load Balancer Logs including access and error detail.
When these logs run on high-traffic subnets or services, they can produce millions of entries per hour, significantly increasing:
- Logging costs
- Object Storage usage
- Logging Analytics ingestion charges
Even small environments can see a 5× to 10× cost increase if logging is misconfigured.
Why It Happens Unexpectedly
Logging often gets enabled temporarily for troubleshooting and is never turned off.
Common root causes include:
Logging enabled at VCN-level, capturing all subnets
DNS logging applied to multiple zones
Load balancer access logs left running on all LBs
Long retention periods (30–90 days)
Very high sampling rates (1-second logs)
All these create unnecessary log volume and high recurring costs.
Real Symptoms We See
Sudden spikes in OCI monthly bills
High Logging Analytics ingestion alerts
Large Object Storage consumption
Slow log searches due to huge datasets
Difficulty troubleshooting network issues
How to Control the Costs (Quick Fixes)
Enable Flow Logs only where required
DMZ → Yes
DB subnet → No (unless debugging)
Reduce sampling rate from 1 second to 20–30%
Lower retention periods to 7–14 days
Disable DNS logs unless specifically needed
Review Load Balancer logs and enable them only for troubleshooting
Enable cost alerts for Logging Analytics ingestion to avoid surprises
Conclusion
Logging is a critical component of observability and security in OCI, but when enabled without proper scope and lifecycle management, it can quickly become a major cost driver. Most logging-related cost spikes are not caused by increased workload demand, but by temporary troubleshooting configurations that remain active longer than intended.
By enabling logs selectively, adjusting sampling and retention settings, and continuously monitoring logging-related costs, organizations can maintain operational visibility while avoiding unexpected billing increases. Proactive logging governance ensures that OCI environments remain both cost-efficient and operationally effective.
