Hi,
please find useful information related to ELM functionality in below link,
https://help.sap.com/saphelp_crm60/helpdata/en/46/32ad40ff4914dce10000000a155369/content.htm
http://sapinsider.wispubs.com/Assets/Blogs/2011/January/How-External-List-Management-works
Hope it helps,
regards,
PD