Mark,
From July 2000 of mcpressonline
http://www.mcpressonline.com/application-software/ibm/the-as/400-and-ibm
s-db2-datajoiner.html
So why does your AS/400 need additional software for heterogeneous
database access? DB2 UDB for AS/400 (and the IBM DB2 family) has long
supported the X/Open Distributed Relational Database Architecture (DRDA)
standard for remote database access and interoperability. Today, AS/400
customers can use DRDA to access the other DB2 products running on UNIX
and Intel servers, but not third-party databases.
Other database vendors such as Oracle and Sybase have actually delivered
tools based on DRDA. Unfortunately, they have chosen to support only
part of the standard: They implemented the DRDA specs that enable them
to access data in other databases, but they have chosen not to support
the DRDA support that would allow DRDA-compliant databases (e.g., DB2
UDB for AS/400) to access and update their data. That's where DB2
DataJoiner comes into play in AS/400 land. The middleware portion of the
product can
speak to both DRDA and non-DRDA interfaces (Oracle SQL*Net, ODBC, etc.)
supported by other databases.
Think of DB2 DataJoiner as a language interpreter. Your AS/400
applications will send DRDA requests to DataJoiner, and DataJoiner will
translate that request into a language that the third-party databases
can understand.
Conversing with DataJoiner from the AS/400 is as simple as issuing an
SQL request.
The SQL-based interface makes it very easy to access DB2 DataJoiner from
just about any AS/400 application. With the DB2 UDB precompilers, you
can embed SQL statements in RPG, C, C++, and COBOL applications on the
AS/400. The following is a sample of the embedded SQL that you would use
to read an Oracle table with DataJoiner from an AS/400 application:
EXEC SQL CONNECT TO DJOINDB;
EXEC SQL SELECT CUSTPREF INTO :LOCPREF FROM ORCUSTOMER WHERE CUSTID=22;
This example assumes that you have already completed the needed
DataJoiner setup. (I cover this setup in my sidebars at www.
midrangecomputing.com/mc.)
If you have used DRDA to access data on another AS/400 or another DB2
server in the past, you'll notice that the SQL interface is exactly the
same. These embedded SQL statements can coexist with an existing
application that is using the native (i.e., non-SQL) AS/400 database
interfaces, so you do not need to switch the entire application over to
SQL. Other SQL-based interfaces on the AS/400-such as Net.Data, Java
Database Connectivity (JDBC), Call Level Interface (CLI), and
DataPropagator-can also leverage DataJoiner for heterogeneous database
access.
When you look at DB2 DataJoiner closely, you'll quickly notice that it
doesn't run on the AS/400; it runs only on Microsoft Windows NT and UNIX
servers. You can easily install DB2 DataJoiner on the same NT or UNIX
server that's hosting the third-party database that you need to access.
A more viable option is to install the product on the Integrated
Netfinity Server for AS/400 (INS) to give you tighter integration
between the AS/400 and DB2 DataJoiner.
midrange.com
