Within 15 days my database log file size become a 15 GB+ please help to reduce size of database.
are you taking log backups?
not taking any backup.
You need to make regular backups of the database and the log. If your database is using Full or Bulk-logged recovery, the log will continue to grow without regular log backups.
If you do not need to restore your database to a point in time, then you can change to Simple recovery and reduce log growth. You can still have log growth if you have single transactions that change a lot of data (for instance, updating a large table with millions of rows).