Recently for a customer we migrated Oracle database to SQL Server 2008 using SSMA tool (SQL Server Migration Assistance for Oracle).The SSMA tool also creates a SYSDB database on the SQL Server instance which contains the replica of Oracle system function that do not exists in SQL Server.
Now the scenario is following statements cannot be executed inside the user defined function of SQL Server:
1) Raising errors or exceptions handling
2) Print statements
3) DML operations like UPDATE, INSERT, DELETE that modify tables, except for local table variables
4) A call of a stored procedure