Actuallly i am new to salesforce and i cant understand how i do this..i make a custom object of name error log and make 4 custom fields in that namly  1.Parent Record Id  and Parent Record Name of text type and  Error Details of  Type  Long Text Area and the last one is  Parent Record which is a  Formula Field: URL.. 
Now i have to pass two arguments in my method one is list<Account > and other is list<contact> ..now what i am doing in my account list i am populated some record but what i need that like i am populating 10 records then some them are populated with id but some of them not..so as we know that every record has id then how can i poluatated record without id .....then after poplating theste records i have to Update that records where Id is populated and insert the records where Id is not populated. (Use Database.upsert ) ... now at last i have to Check the Database.upsert result and if there is any error with any of the record then it create a new record of Error Log (custom object) for each error.
and in my list of contact i have to hold the new contact records and these contact i have to add to those account which are success...like i have 2 contact in my list<contact> then these 2 contact add to all account record like i have 4 succes account record after database.upsert the 2 contact add to each and at last they became 8....then how can i polate record and cause error by which i save these error to my custom object ..for every new error a new record is added ..