To understand the iSeries, you need to know IFS

I have to admit I am pretty new to the iSeries. I have used Windows most of my computing life. I try to stray outside my comfort zone and use linux. Truth be told that doesn't happen much. That just makes my job all that much sweeter. I get to play with an iSeries everyday!

In windows, files seem to be pretty basic. They are data. In the iSeries world they would be Physical Files or PF. On the iSeries you also have Logical Files or LF. A Physical File is a generic database file. A Physical File could also be a member or format. It is where the data is. Physical Files can also be referred to as Disk Files. Full-procedural file processing will access the disk files.

Data Definition Services or DDS are LF in that they define your database files. In come the RPG programs to access the Physical Files. This works only if you have your library list set correctly. This key point I can't stress enough.

Some of the most standard libraries on the iSeries are:

• QSYS-      System Lib    Type SYS
• QHLPSYS-System Lib    Type SYS
• QUSRSYS-System Lib    Type SYS
• DBU70    -System Lib    Type SYS  Database Utility
• QTEMP   -Temp   Lib    Type CUR This will change of course.
• QGPL      -GeneralLib    Type USR  this is the IBM general purpose library
• USRTD    -TruckDrivLib  Type USR  my library

These are just a few of the Libraries we use. The order of the types is pretty standard. One key thing to note is that when you execute a program is how your library list is set. This is because the system when needing files will search your Lib list til it finds a file your program has requested. Did you notice the "a" in the last sentence? You can have a file with the same name in different libraries. Totally different files with the same name. This can be a problem if the file your program accesses is not the one you intended. Undesired results can and will happen.

Well time to get off the soap box.  Thanks for listening.

Did this help? I look forward to your comments.