I can't answer your JPA vs. JDO question...

But let me assure you that the RDBMS built into IBM i v6.1 is as
rational as anything else out there and arguably more relational than
anything else out there. (Based upon how closely it comes to the SQL
standards)

What's confusing is that the RDBMS built into the system has roots
going back to before SQL or many modern features of a RDBMS such as
transaction isolation and the ability to have FK and check constraints
built into the DB. Given the priority IBM places on backwards
compatibility, the use of the more modern features is optional and the
system maintains two methods of data access: traditional and SQL.
http://publib.boulder.ibm.com/infocenter/iseries/v6r1m0/topic/rzatc/rzatcterminology.htm

But the two methods are interchangeable.

You can create a table using the traditional Data Description Language
(DDL) known as Data Description Specification (DDS) and query it using
SQL. Similarly you can use SQL DDL to create a table and use RPG or
COBOL record level access (RLA) to read and write to it. IBM even
provides RLA classes for Java to make use of.

The tool provided by IBM to extract SQL DDL for a table works on
tables created with SQL DDL or traditional DDS. Thus, it's often used
to move from DDS to SQL DDL.

It as easy (arguably easier) to create a modern DB app that uses the i
as it is to use any other DB. It's a little more difficult to built
an SQL based app on a heritage DB as many don't have FK or check
constraints and often have short column names. Long column names
can be added without impacting any heritage applications. Constraints
can also be added, though you must take into account that heritage RPG
code might not check for CRUD operations to fail.

For help with SQL vs. traditional, consider joining the MIDRANGE mailing list.
http://lists.midrange.com/mailman/listinfo/midrange-l

HTH,
Charles

On Fri, Aug 19, 2011 at 5:34 AM, MANUEL FIDALGO SICILIA
<manuel.fidalgo@xxxxxxxxxxxxxxxxxx> wrote:
Dear all,

Foremost, I would like to say that I'm new to the AS/400 world so sorry
if I ask stupid things...

At work we are using v6r1m0 and we would to write some Java programs
using the AS/400 as database.

The problem comes when deciding what persistence engine to use: I can't
see clearly if the AS/400 is relational or non-relational and I would
like to know which should be better JPA or JDO. I know some people use
JPA but I'm wondering if it is not better to use JDO which has support
for both relational and non-relational and if JPA will have performance
problems because it is made for relational.

So what do you think? JDO or JPA? Or maybe just jdbc!

Thanks in advance!



Jose Manuel

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