User Space (Iseries/AS400 Object)

User Spaces

User spaces are objects that consist of a collection of bytes used for

storing user-defined information.

They are permanent objects that are located in either the system domain or the user domain. They have an object type of *USRSPC and a maximum size of 16MB.

A user space is used when information about more than one object is being requested. For example returning either a list of members in a file or objects in a library.

APIs that return information to a caller generally return the information in a user space (used by list APIs) or a receiver variable (used by retrieve APIs).

Most lists returned by APIs are made up of a series of entries where each entry is a data structure.

When you use one of the list APIs, the parameter list requires that you name the user space that will be used.

You can use these APIs to:

o Create and delete user spaces

o Change and retrieve the contents of user spaces

o Change and retrieve information about user spaces

Following are some of the advantages of using user spaces:

o User spaces can be automatically extendable.(16 MB)

o User spaces can be shared across jobs.

o User spaces can exist across IPLs.

The disadvantage of using a receiver variable when it may be too small for the amount of data being returned is that the API must be called again to receive the remaining data.

QSYLOBJP - List Objects that Adopt Owner Authority

QUSCRTUS - Create User Space

QUSPTRUS - Retrieve Pointer to User Space

QUSROBJD - Retrieve Object Description

When to use USRSPC & Data queues?

Use user queues when:

- You have a programming background in or prefer to program in C or

MI.

- You need the additional performance of an API for creating and

deleting and MI instructions for manipulating entries.

- You do not need to create a user-domain queue into a library where

the QALWUSRDMN system value does not permit user-domain user

objects when at security level 40 or 50.