IBM DS8000 - ADDITIONAL INFORMATION, User Manual, Page: 58 / 250

Table 2. Comparison of licensed functions (continued)
Licensed function Description Advantages Considerations
Global Mirror Asynchronous copy Nearly unlimited
distance, scalable,
and low RPO. The
RPO is the time
needed to recover
from a disaster; that
is, the total system
downtime.
RPO might grow
when link bandwidth
capability is
exceeded.
z/OS Global Mirror Asynchronous copy
controlled by System
z host software
Nearly unlimited
distance, highly
scalable, and very
low RPO.
Additional host
server hardware and
software is required.
The RPO might grow
if bandwidth
capability is exceeded
or host performance
might be impacted.
Parallel access volumes and IBM HyperPAV
The use of the parallel access volumes (PAV) feature enables a single System z or
S/390 host to simultaneously process multiple I/O operations to the same logical
volume, which can help to significantly reduce device queue delays. This is
achieved by defining multiple addresses per volume.
With dynamic PAV, the assignment of addresses to volumes is automatically
managed to help the workload meet its performance objectives and minimize
overall queuing.
You must configure both your storage unit and operating system to use PAVs. You
can use the logical configuration definition to define PAV-bases, PAV-aliases, and
their relationship in the storage unit hardware. This unit address relationship
creates a single logical volume, allowing concurrent I/O operations.
For System z or S/390 hosts, the storage unit supports concurrent or parallel data
transfer operations to or from the same volume from the same system or system
image. PAV software support enables multiple users and jobs to simultaneously
access a logical volume. Read and write operations can be accessed simultaneously
to different domains. (The domain of an I/O operation is the specified extents to
which the I/O operation applies.)
You can enhance PAV by adding the IBM HyperPAV feature which allows you to
use alias addresses to access any base on the same control unit image per I/O
base.
CKD extended address volumes - 3390 Model A
The DS8000 supports CKD extended address volumes and provides increased
storage capacity with 3390 Model A.
3390 Model A is intended as replacement for 3390 Model 3 and 3390 Model 9.
Volumes can be converted between 3390 Model 3, 3390 Model 9, and 3390 Model A
if the volume sizes are within 3390 Model 3 and 3390 Model 9 limits. 3390 Model
3, 3390 Model 9, and 3390 Model A volumes can be increased in size to their
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DS8000 User’s Guide
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