The orphaned shared agent data notes store agent log information.
These notes are created when agents are run in strange ways, or when agents are run and then saved while they are being run etc.
You can fix this problem by running a Compact Agent Tool program available from Lotus.
Search for this on knowledge base or on the lotus support web site.
Document code 2655.
http://www-1.ibm.com/support/docview.wss?rs=899&contq1=2655&uid=swg21101603&loc=en_US&cs=utf-8&lang=en+en