Sybase Database Migration from 11.5 to 15

I have to migrate the Sybase Database from 11.5 version to 15. I would like to know few things mentioned below - i) What are the neccessary steps I need to follow in this migration. ii) What are the changes required for table, Stored Proc, etc., for this change to work as per the current execution? iii) Any bottle necks if exist for this transiton Note :- We have a Unix server that executes these procs with the help of Perl Script? Thanks Utkarsh