Data Monitoring / SQL Server Availability & Capacity
SQL Server: Database file space versus volume space
A nearly full data file still has room to grow on disk, while another file cannot. Measure used file space, allocated file size, maximum size and volume free space separately.
Environment and inputs: SQL Server operational monitoring; availability groups, SQL Agent and host-level metrics depend on edition, service and deployment.
Failure scenario
A nearly full data file still has room to grow on disk, while another file cannot. Confirm the cause before choosing a fix.
Evidence to collect
Measure used file space, allocated file size, maximum size and volume free space separately. Record the time, affected scope and a healthy comparison interval.
Fix the confirmed cause
Choose the relevant capacity action and avoid treating these four measurements as interchangeable. Write the expected result first. Change one relevant setting at a time.
Check the result and hand over
Repeat the check for database file space versus volume space using the same scope and a representative interval. Check that the symptom is resolved, expected records are present and downstream results are correct. If coverage, correctness or latency worsens, restore the recorded configuration through the agreed rollback process.
Scope and precautions
Prefer read-only access and limit queries to the relevant period or dataset. This example has not been tested on your systems. Test changes in an approved environment. Keep credentials and sensitive data out of shared evidence.