When mapping a stored procedure OA reorders the parameters of the procedure and uses this order to configure the store command when executing the procedure. This is a problem with providers that bind parameters by position by default, e.g. Oracle.DataAccess. This is a very dangerous, hard to detect silent bug, I only hit it because OA switched two of my parameters that were of different type (varchar2 and date) thus execution failed with an obscure exception (ORA-01841). If the switched parameters are of the same type then the only symptom is bad data returned from the proc.
I can think of two possible fixes here (either should fix the problem but I think both should be implemented)
1. Keep parameters in db order. As requested here: http://www.telerik.com/community/forums/orm/general-discussions/stored-procedures-in-orm-parameters-moving-around.aspx
2. If I see it correctly OA uses the ODP.NET package provided by Oracle (I'm using 188.8.131.52). Set the OracleCommand.BindByName property to true when setting up the store command to force binding parameters by name.
This issue is tested with OA version 2012.2.607.1