HCOSS converts DB2 functions and special registers to SQL Server functions or special registers automatically, using a set of defaults to map each DB2 function or special register to a corresponding SQL Server function or special register.
If you want to convert any of your DB2 database functions or special registers to SQL Server database functions or special registers using settings other than the defaults mapped by HCOSS, you can customize them.
Also from the Custom SQL Name Mappings tool, you can add DB2 functions and special registers defined in your DB2 database that are not represented in your SQL Server database.