If you don't care about recovering any failed transactions, stop the WebSphere appserver instance hosting LiveCycle, go to its transaction log folder and delete any files in it. In our AIX environment, where the appserver instance hosting LiveCycle is named "lc1", the transaction log is located at:
/opt/WebSphere/AppServer/profiles/AppSrv01/tranlog/yourcellname/yournodename/lc1/transaction/tranlog
You might also want to clean up:
/opt/WebSphere/AppServer/profiles/AppSrv01/tranlog/yourcellname/yournodename/lc1/transaction/partnerlog