RPG numeric types mapping to SQL types

I've created a module that will be placed in a service program, and
created an SQL Function that makes the service program module callable
from within an SQL view.  The problem is that, as you can see from the
prototype, I am using packed decimals, which translate to DECIMAL
types in SQL.  Even if I use fields from a database file that are
packed decimal, I have to CAST them in SQL to DECIMAL.  What RPG
number type can I use to avoid this CASTing in SQL?

Prototype follows:

     D DLMCCalc        PR             7P 2
     D  MedNecLvl                     1P 0 Const
     D  EMLvlCharg                    7P 0 Const
     D  Acronym                       3A   Const
     D  Family#                       9P 0 Const
     D  Member#                       2P 0 Const
     D  SvcDate                        D   Const

The SQL function creation was done like this:

Create Function DMart.CalcDCost 
(       DEC (1,0), 
        DEC (7,0),
        CHAR (3),
        DEC (9,0),
        DEC (2,0),
        DATE)
Returns DEC (7,2)
Language RPGLE
Deterministic
no sql
returns null on null input
no external action allow parallel
simple call
External Name 'DMART/DL_FUNC(DLMCCALC)';

Now, the pain in the rear, is that to call the function, I have to
code it in the SQL as follows:

DMart.CalcDCost(Cast(Log.MedNecLvl As DECIMAL(1,0)),
                Cast(Log.EMLvlCharg As DECIMAL(7,0)),
                Log.SysAcr,
                Cast(Log.Famly# As DECIMAL(9,0)),
                Cast(Log.Membr# As DECIMAL(2,0)),    
                Log.Date1Post)


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