Quest Quick Connect execution transaction database log file (MSSQL) growing exponentially

HI I have a quick connect - sync engine and express for active directory 64 bit installed (version 5.3.0).

I have a current issue where the execution transaction database log file (MSSQL) has been growing exponentially around 20 GB every week suddenly in the last three months. This has consumed all my hard disk space. Normally the log database transaction file does not grow.  

what could be the cause and how to stop? there was no change in configuration or SQL

thanks

Shivabalan