SQL Server ldf file size keeps increasing, but there are no changes in the mdf file

[CrazyPotato]

I encountered strange things, the .ldf file size is increasing 50G in one hour, and in two hours, it increased by 100 G.

But the .mdf has no big changes, such as lot of entry writes.

Do you experts help me find what kind of reason can trigger such scenario?

My database is SQL Server Express edition.

My database under simple recovery mode

I tried to run DBCC opentran, but found no hanging transaction

I tried to run DBCC shrinkfile(db_log, 1), but the log file size didn't shrink

[#2]

Please make sure that database maintenance (jobs, maintenance plans or scripts) are not creating those increase in the size on the database log. Maybe on those scripts you are updating statistics with FULL SCAN or rebuilding indexes, all these are logged operations.

Making frequent log backups of the database can prevent the log from increasing its size or switch the database to SIMPLE recovery model.