OL 9 must notify the system administrator (SA) and information system security officer (ISSO) (at a minimum) when allocated audit record storage volume reaches 75 percent utilization.
If security personnel are not notified immediately when storage volume reaches a maximum of 75 percent utilization, they are unable to plan for audit record storage capacity expansion. The notification can be set to trigger at lower utilization thresholds at the ISSO's discretion.
How this relates to the STIG checklist: STIG vs SCAP benchmark.