IBM i provides several small object types that programs can use to share state and coordinate work. Data areas, data queues, and user spaces are three of the most practical ones.
Why this matters
They solve a common problem: sometimes a program needs to pass a value, a signal, or a block of information without using a full database table.
Core concepts
Data areas
A data area is a small named storage object for a simple value or control flag.
Data queues
A data queue lets one job send a message to another job in an orderly way.
User spaces
A user space can hold larger structured data when a simple value is not enough.
Practical communication
Together, these objects help jobs coordinate without inventing a separate messaging platform.
Practical example
A background job can write a status flag into a data area, place a message on a data queue, and let an operator-facing program react without polling a database table.
Common mistakes
- Using the wrong object type for the size or lifespan of the data.
- Treating shared objects as if they were automatically thread-safe everywhere.
- Overcomplicating simple coordination problems that a small object could solve.
Where this fits in the series
If you want the platform foundation first, read the pillar article, What Is AS400 (IBM i)? A Complete Beginner’s Guide.