ABCs of z/OS System Programming Volume 3 - IBM Redbooks

3.7 HyperPAV implementation
Applications
do I/O to base
volumes
Applications
do I/O to base
volumes
Applications
do I/O to base
volumes
Applications
do I/O to base
volumes
z/OS Image
UCB 0801
UCB 08F0
UCB 0802
z/OS Image
UCB 08F0
UCB 0801
UCB 08F1
UCB 08F3
UCB 0802
UCB 08F3
UCB 08F2
UCB 08F1
UCB 08F2
Figure 3-7 HyperPAV implementation using a pool of aliases
Storage Server
Logical Subsystem (LSS) 0800
Alias UA=F0
Alias UA=F1
Alias UA=F2
Alias UA=F3
Base UA=01
Base UA=02
HyperPAV feature
With the IBM System Storage DS8000 Turbo model and the IBM server synergy feature, the
HyperPAV together with PAV, Multiple Allegiance, and support for IBM System z MIDAW
facility can dramatically improve performance and efficiency for System z environments.
With HyperPAV technology:
► z/OS uses a pool of UCB aliases.
► As each application I/O is requested, if the base volume is busy with another I/O:
– z/OS selects a free alias from the pool, quickly binds the alias device to the base
device, and starts the I/O.
– When the I/O completes, the alias device is used for another I/O on the LSS or is
returned to the free alias pool.
If too many I/Os are started simultaneously:
► z/OS will queue the I/Os at the LSS level.
► When an exposure frees up that can be used for queued I/Os, they are started.
► Queued I/O is done within assigned I/O priority.
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Chapter 3. Extended access volumes 65