When the installation does not use any other method to define a limit, then exec and spawn handle limits after an identity change. After an identity change, an exec sets hard and soft limits to z/OS® UNIX values. The change to z/OS UNIX values can also be accomplished by using a setuid() followed by an exec().

Spawn() can also cause an identity change. A spawned child that was created with a different identity than the parent using InheUserid or _BPX_USERID sets the hard and soft limits to the z/OS UNIX values for the new identity. A forked child with no identity change inherits the settings of the parent.

Task-level security (pthread_security or _login) causes spawn to use the limits of the new identity.

Resources values that processes receive when they are dubbed a process use the RACF® profile to determine the hard limit if it is higher than the soft (current) limit. It is also used when processes are initiated by a daemon process using an exec after setuid(). In this case, both the RLIMIT_AS hard and soft limits are set to the address-space-size value.