MSSQL-SPACE-001 · Disk or transaction log running out of space

Severity	Confidence	Permission	Applies to
High	Hint · Confirmed below 5% free / above 90% log used	VIEW SERVER STATE (2022+: VIEW SERVER PERFORMANCE STATE)	SQL Server 2017+, Azure SQL MI, RDS, Azure SQL Database

What it checks

• Volumes that hold database files (sys.dm_os_volume_stats) with less than 15% free (volume_hint_pct).
• Transaction logs more than 75% used (log_hint_pct, active log ÷ log size from sys.dm_db_log_stats) whose log_reuse_wait_desc says something is preventing reuse (anything other than NOTHING or CHECKPOINT).

On Azure SQL Database there are no volumes: it checks the space used against the database max size (DATABASEPROPERTYEX(..., 'MaxSizeInBytes'), same 15% / 5% thresholds) and the log of the connected database. Hyperscale has no max size and is skipped.

Why it matters

A full volume or a full log stops writes in every affected database. A log that can't be reused keeps growing until it hits one of them.

Next action

Act on log_reuse_wait_desc:

Value	What to do
LOG_BACKUP	Take log backups (or switch to SIMPLE if point-in-time restore isn't needed)
ACTIVE_TRANSACTION	Find the open transaction: DBCC OPENTRAN
REPLICATION / AVAILABILITY_REPLICA	Check the log reader or the secondary replica

Limitations

A snapshot tells how full things are, not how fast they grow. Projecting when a volume fills up needs history.