A beginner-friendly guide to understanding common file object types on IBM i

Introduction

IBM i organizes data and objects using a powerful object-based architecture. For beginners, the different types of files can be confusing at first - especially when terms like PF, LF, or DTAQ start showing up in menus and commands. This guide breaks down the most commonly used IBM i file types in simple terms, with relatable examples to help you understand their roles and how they fit into everyday tasks.

1. PF - Physical File

What It Is: A PF (Physical File) stores actual data in rows and columns, much like a table in a relational database.

Think of It Like: A spreadsheet with rows of data you can read and update.

Use Case: Customer records, inventory tables, or transaction logs.

Create Example: CRTPF FILE(MYLIB/CUSTOMERS) SRCFILE(MYLIB/QDDSSRC)

2. LF - Logical File

What It Is: An LF (Logical File) is like a virtual view or index on a PF. It doesn't store data, but provides alternate ways to access and sort it.

Think of It Like: A filter or sorted view of your spreadsheet.

Use Case: Sorting customer records by ZIP code or selecting only active accounts.

Create Example: CRTLF FILE(MYLIB/CUSTBYZIP) SRCFILE(MYLIB/QDDSSRC)

3. SAVF - Save File

What It Is: A SAVF (Save File) is used to hold a backup of objects such as programs, libraries, or data files. It is especially useful for moving data between systems.

Think of It Like: A ZIP file containing backups or installable.

Use Case: Backing up a program or transporting it to another system.

Create Example: CRTSAVF FILE(MYLIB/MYSAVF)

4. DTAQ - Data Queue

What It Is: A DTAQ (Data Queue) allows programs to send messages or data to each other asynchronously.

Think of It Like: A shared mailbox where one program sends data and another picks it up later.

Use Case: Order processing systems where one job submits and another fulfills.

Create Example: CRTDTAQ DTAQ(MYLIB/ORDERSQ) MAXLEN(256)

5. OUTQ - Output Queue

What It Is: OUTQ holds spool files (printed output) waiting to be printed or viewed.

Think of It Like: A print queue in Windows.

Use Case: Holding reports, invoices, or logs before printing or archiving.

Create Example: CRTOUTQ OUTQ(MYLIB/SALESOUTQ)

6. CMD - Command Definition File

What It Is: CMD defines custom commands that users can run just like system commands.

Think of It Like: A shortcut or macro for a complex operation.

Use Case: Running a common cleanup task or triggering a job.

Create Example: CRTCMD CMD(MYLIB/MYCLEANUP) PGM(MYLIB/CLEANUPPGM)

7. DTAARA - Data Area

What It Is: A DTAARA is a small memory space used to store a single value or flag.

Think of It Like: A global variable or config setting.

Use Case: Storing the last run date of a job or a system flag.

Create Example: CRTDTAARA DTAARA(MYLIB/LASTRUNDATE) TYPE(*CHAR) LEN(10)

Conclusion

IBM i file types may sound technical at first, but they each serve a clear purpose once you know how they work. Whether you're managing data (PF/LF), transferring objects (SAVF), automating workflows (DTAQ), or generating output (OUTQ), these object types are essential building blocks of the IBM i platform.

Understanding these will not only help you navigate IBM i confidently but also empower you to troubleshoot and automate tasks with more clarity.