Why should you care?

Full disks and slow logs cause outages. Knowing which file grew tells you whether to add space or fix a long transaction.

See it live — copy this example

Run in SQL Server Management Studio (SSMS) or Azure Data Studio.

USE DataVerse;
SELECT
    df.name AS LogicalName,
    df.type_desc,
    df.physical_name,
    CAST(df.size * 8.0 / 1024 AS DECIMAL(10,2)) AS SizeMB
FROM sys.database_files AS df;

What happened?

• sys.database_files lists logical names, ROWS vs LOG, OS path, and size in MB.
• You see exactly where your database stores bytes on disk.

Practice next

1. USE your database and run the query.
2. Note the .mdf and .ldf paths.
3. In SSMS, right-click your database → Properties → Files and compare.
4. Add df.max_size and df.growth to the SELECT list.
5. Compare sizes after creating a large test table (then drop it).

Remember

Data file holds tables; log file holds recovery records. sys.database_files shows path and size. Watch disk space on those paths.

Log full during big import

A DataVerse ETL left an open transaction and the .ldf filled the disk.

Outcome: Team fixed the transaction and moved log to a larger volume.