KB926103 - The size of the SystemCenterReporting database grows quickly after you install the BizTalk 2006 Server management pack on a Microsoft Operations Manager 2005 server
KB926103 - https://support.microsoft.com/?id=926103
SYMPTOMS
After you install the Microsoft BizTalk Server 2006 management pack on a Microsoft Operations Manager (MOM) 2005 server, you notice that the size of the SystemCenterReporting database grows quickly.
Please refer to the KB article link above for the workaround to this issue.