file400

IBM i record level access for Python 3. (beta)

Background

We have a lot of python modules written for iseries python 2.7 that uses the file400 module.

When I planned to migrate to Python 3.6 pase for i, my biggest concern was the database access, and the only option was the ibm-db-dbi module.

We have an Ubuntu box with postgres, that runs the same python programs.
It has a layer on top of psycopg2 that emulates file400.
Db2 database changes is copied to the Ubuntu postgres database using journals, and when the IBM i is unavailable during full backup a few hours every week, this Ubunto box takes over. This has been running for several years without any performance problems with the file400 layer on the Ubuntu box.

I decided to use this same layer on top of ibm-db-dbi on the IBM i, but the performance hit was to big.

I then converted the _db2 module from iseries Python 2.7 and used that instead of ibm-db-dbi, but it didn't make big difference.

Now I have rewritten the file400 module, and with this the performance is at least as good as on Python 2.7.

Installation

You will have to install an ile service program called reclevacc and a python c extention module named file400.so
Download file400.so.zip and reclevacc.savf.zip
Unpack the zip files on your pc.
Transfer file400.so to site-packages (/QOpenSys/pkgs/lib/python3.6/site-packages)
Create a lib called python3
Transfer reclevacc.savf to python3 (/QSYS.LIB/PYTHON3.LIB)
Run RSTOBJ OBJ(RECLEVACC) SAVLIB(PYTHON3) DEV(*SAVF) SAVF(PYTHON3/RECLEVACC)

Use it as in python2.7 (a few of the functions has been removed)

from file400 import File400  
f = File400('myfile', 'r')  
f.posb((first_key, second_key))  
while f.readne():  
    print(f._first1)

The db2 module is also available, though it's probably better to use ibm-db-dbi.
Install as with file400
Example on how to use it.

import _db2 as db2  
con = db2.connect(servermode=False, autocommit=True, sysnaming=True)  
for row in con.execute("select col1, col2 from myfile"):  
    col1, col2 = row  
    print(col1, col2)

In case you would like to do the compilation your self.

_db2.c
Compile
gcc -pthread -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -O2 -g -maix64 -I/QOpenSys/pkgs/include -I/python3/source/include -I/QOpenSys/pkgs/include/python3.6m -c _db2.c -o build/temp.os400-powerpc64-3.6/_db2.o
link
gcc -pthread -shared /QOpenSys/pkgs/lib/python3.6/config-3.6m/python.exp /QOpenSys/lib/libdb400.a build/temp.os400-powerpc64-3.6/_db2.o -o build/lib.os400-powerpc64-3.6/_db2.so

file400.c
Compile
gcc -pthread -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -O2 -g -maix64 -I/QOpenSys/pkgs/include -I/python3/source/include -I/QOpenSys/pkgs/include/python3.6m -c file400.c -o build/temp.os400-powerpc64-3.6/file400.o
link
gcc -pthread -shared /QOpenSys/pkgs/lib/python3.6/config-3.6m/python.exp /QOpenSys/lib/libiconv.a build/temp.os400-powerpc64-3.6/file400.o -o build/lib.os400-powerpc64-3.6/file400.so

RECLEVACC ILE program
CRTCMOD MODULE(PYTHON3/RECLEVACC) SRCSTMF('/python3/source/reclevacc.c') SYSIFCOPT(*IFS64IO) LOCALETYPE(*LOCALEUTF) TERASPACE(*YES *TSIFC) STGMDL(*TERASPACE) DTAMDL(*P128)

CRTSRVPGM SRVPGM(PYTHON3/RECLEVACC) EXPORT(*ALL) STGMDL(*TERASPACE)

License

perg/file400

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