Connecting to IBM AS400 server for database operations hangs

Question

I\'m trying to talk to an AS400 in Python. The goal is to use SQLAlchemy, but when I couldn\'t get that to work I stepped back to a more basic script using just ibm_db inste

Answer 1

The README for ibm_db_sa only lists DB2 for Linux/Unix/Windows in the "Supported Database" section. So it most likely doesn't work for DB2 for i, at least not right out of the box.

Since you've stated you have IBM System i Access for Windows, I strongly recommend just using one of the drivers that comes with it (ODBC, OLEDB, or ADO.NET, as @Charles mentioned).

Personally, I always use ODBC, with either pyodbc or pypyodbc. Either one works fine. A simple example:

import pyodbc

connection = pyodbc.connect(
    driver='{iSeries Access ODBC Driver}',
    system='11.22.33.44',
    uid='username',
    pwd='password')
c1 = connection.cursor()

c1.execute('select * from qsys2.sysschemas')
for row in c1:
    print row

Now, one of SQLAlchemy's connection methods is pyodbc, so I would think that if you can establish a connection using pyodbc directly, you can somehow configure SQLAlchemy to do the same. But I'm not an SQLAlchemy user myself, so I don't have example code for that.

UPDATE

I managed to get SQLAlchemy to connect to our IBM i and execute straight SQL queries. In other words, to get it to about the same functionality as simply using PyODBC directly. I haven't tested any other SQLAlchemy features. What I did to set up the connection on my Windows 7 machine:

• Install ibm_db_sa as an SQLAlchemy dialect
  You may be able to use pip for this, but I did it the low-tech way:

  1. Download ibm_db_sa from PyPI.
     As of this writing, the latest version is 0.3.2, uploaded on 2014-10-20. It's conceivable that later versions will either be fixed or broken in different ways (so in the future, the modifications I'm about to describe might be unnecessary, or they might not work).
  2. Unpack the archive (ibm_db_sa-0.3.2.tar.gz) and copy the enclosed ibm_db_sa directory into the sqlalchemy\dialects directory.

• Modify sqlalchemy\dialects\ibm_db_sa\pyodbc.py
  

  • Add the initialize() method to the AS400Dialect_pyodbc class
    The point of this is to override the method of the same name in DB2Dialect, which AS400Dialect_pyodbc inherits from. The problem is that DB2Dialect.initialize() tries to set attributes dbms_ver and dbms_name, neither of which is available or relevant when connecting to IBM i using PyODBC (as far as I can tell).
  • Add the module-level name dialect and set it to the AS400Dialect_pyodbc class

Code for the above modifications should go at the end of the file, and look like this:

    def initialize(self, connection):
        super(DB2Dialect, self).initialize(connection)

dialect = AS400Dialect_pyodbc

Note the indentation! Remember, the initialize() method needs to belong to the AS400Dialect_pyodbc class, and dialect needs to be global to the module.

Finally, you need to give the engine creator the right URL:

'ibm_db_sa+pyodbc://username:password@host/*local'

(Obviously, substitute valid values for username, password, and host.)

That's it. At this point, you should be able to create the engine, connect to the i, and execute plain SQL through SQLAlchemy. I would think a lot of the ORM stuff should also work at this point, but I have not verified this.