MS SQL database includes MDF file and LDF file.
MDF is actual data of an application and LDF file is a transaction log file which records the queries and the result. It can be optimized through "Shrink option for the file.
<How To Check Size of LDF and Reduce the size of the file>
1. Run SQL Management studio as administrator
2. Copy the below query and click on [Execute]
3. Confirm the size of BioStar_log
4. Stop BioStar Server
5. Mouse right click on BioStar DB name and go Tasks>Shrink>Files
6. Click File Type>Log and click on [OK]
7. Copy the below query and click on [Execute] and check the result.