Since Quickbooks is an application that uses SQL database, the database server has a transactional log file. The Quickbooks TLG file is the transactional database log file and it can sometimes grow larger than the actual data file. Large TLG files hamper performance.
Do not erase the TLG file under any circumstances.
The easiest way to shrink the TLG file is to back up Quickbooks from within the application.
From the file menu, select create backup.
Follow the instructions to back up Quickbooks and shrink the TLG file.