User spaces

List APIs require a user space for returning information. A user space is an object consisting of a collection of bytes that can be used for storing any user-defined information.

Following are some of the advantages of using user spaces:

User spaces can be automatically extendable.
User spaces can be shared across jobs.
User spaces can exist across IPLs.

To provide a consistent design and use of the user space (*USRSPC) objects, the list APIs use a common data structure. The list APIs are those APIs that generate a list unique to that API. This includes any list API that has a user space parameter, such as the List Spooled Files and List Objects APIs.

General data structure
The list APIs use a general data structure.
Common data structure formats
This topic shows the generic user space layout. Format 0100 shows the format for an original program model (OPM) layout. Format 0300 shows the format for an Integrated Language Environment^® (ILE) model layout. The fields are described in detail after the table.
Example: User space format
This example illustrates the format of a user space. This example does not contain all of the fields in the fixed portion of a user space.
List sections
Each list API provides a input parameter, header, and list data section.

Parent topic: User spaces and receiver variables

Related concepts

User spaces for list APIs

Receiver variables

List APIs overview

Related reference

Example in OPM RPG: Using keys with List Spooled Files API