In DB2, you can use the X'FF' syntax to specify a hexadecimal constant (literal). In SQL Server, you have to use the 0xFF syntax.
DB2:
-- Hex constant SELECT X'1234ABCDEF' FROM sysibm.sysdummy1;
SQL Server:
-- Hex constant SELECT 0x1234ABCDEF;
For more information, see IBM DB2 to SQL Server Migration.