PL/SQL :: Client Server Application That Created Using MS-SQL Server Database

I have a Client Server application that I created using an MS-SQL Server Database (MS-SQL Server 2008 R2 Express).Since MS-SQL Server has wide range (and number) of DATA_TYPEs, I elected to dedicate a few of those DATA_TYPEs to application-specific processing (mainly the MONEY and BOOLEAN DATA_TYPES).

I further decided that within the Client Application that the general processing of a particular field would be determined by the corresponding DATA_TYPE stored in the database.

The DATA_TYPE of a particular field within the SQL Server database and may be determined by querying:

"select DATA_TYPE from INFORMATION_SCHEMA.Columns where ( ( Column_name = 'my_Field' ) and ( Table_Name = 'myTable' ) )"

I also extract/use other DATA_TYPE information as needed/appropriate.

With this information the Client Application can consistently process a MONEY (a DATA_TYPE in MS-SQL Server) differently than perhaps either a DECIMAL or a BIGINT (two other DATA_TYPEs in MS-SQL Server). I have to create the field with the correct DATA_TYPE in the database, but after that I don't have to worry about it.

I am now moving over to an Oracle Database (Oracle Database Express Edition 11g Release 2). And I would like to have the same (or similar) functionality as described above.

Oracle has fewer DATA_TYPES so it is more difficult to tie an application-specific-datatype to an Oracle-database-specific-DATA_TYPE. There simply aren't as many to "sacrifice" to my application-specific-processing. I don't want to treat every NUMERIC field as "the-apps-money-type."

With Oracle I can associate "the-apps-money-type" with, let's say, a NUMERIC(9,2) and then the Client Application will treat all NUMERIC(9,2) as "the-apps-money-type."The Client Application queries the Oracle database for DATA_TYPE, DATA_PRECISION, and DATA_SCALE to make this determination.

But this approach does not appeal to me, suppose that I have other NUMERIC(9,2) fields that are not of "the-apps-money-type." How can I set and then later determine, from the Oracle backend, if the NUMERIC(9,2) field is meant to be used as "the-apps-money-type" or just a regular number?

Is there some way I may create some sort of "sub DATA_TYPE" in Oracle?I considered indicating this in the COMMENTS field that is associated with particular field. Then query for that comment when I process NUMERIC DATA_TYPEs. But the COMMENTS field does not seem to make it into user_tab_columns or all_tab_columns.

(With Oracle SQL Developer one can create/modify/delete the user created tables/fields. COMMENTS may be added to particular fields within a table--these are the COMMENTS that I am referring to above).What I would like to do, and most direct approach to me, would be to somehow create a user defined DATA_TYPE that is simply:

1) a user defined DATA_TYPE name (like, MY_MONEY_TYPE),
2) associated with an Oracle Built-in datatype (like NUMERIC(9,2).

Then when the client application queries user_tab_columns the field may be processed appropriately. If I cannot do that, perhaps there is somewhere else that I may set and subsequently query for this sort of information. What is(are) the most direct way(s) to implement the functionality described above?