HP XP P9000 for Compatible PAV Software Licenses - Manual (Page 5)

1 Overview
This chapter provides an overview of Parallel Access Volumes.
Unless otherwise specified, the term P9000 in this guide refers to the following disk array:
•
P9500 Disk Array
The GUI illustrations in this guide were created using a Windows computer with the Internet Explorer
browser. Actual windows may differ depending on the operating system and browser used. GUI
contents also vary with licensed program products, storage system models, and firmware versions.
Parallel Access Volumes
Parallel Access Volumes run on the P9500 storage system. Parallel Access Volumes enable a single
IBM host computer to issue multiple I/O requests in parallel to a single logical device (LDEV).
Without Parallel Access Volumes, a host system can only initiate and manage one I/O request per
LDEV. Parallel Access Volumes allows users to designate free LDEV addresses as alias devices and
to assign those alias devices to base devices. All I/O requests to the alias devices are treated as
though they were issued to the base device. In this manner, concurrent I/O requests can be handled
simultaneously. Parallel Access Volumes allows the host computer to access data in the storage
system substantially faster.
For more information on the zSeries and S/390 PAV host software feature, see the following IBM
documents:
•
DFSMS/MVS Software Support for IBM Enterprise Storage Server (SC26–7318)
•
DS8000 Performance Monitoring and Tuning (SG24–7146)
•
System/390 Command Reference 2105 Models E10, E20, F10, F20 (SC26–7298)
Base and alias devices
The two types of devices used in Parallel Access Volumes operations are base devices and alias
devices. The P9500 storage system supports up to 256 devices per control unit (CU).
A base device is an LDEV that has a formatted mainframe emulated volume assigned which contains
user data.
CAUTION: A device that has been used as a journal volume in the Continuous Access Journal,
as a volume used for Data Exchange, or as a system disk or migration volume, may not be defined
as a base device.
An alias device is an unassigned LDEV whose unit address can be used as an alias for a base
device. Each alias device must be within the same logical CU image as the base device to which
it is assigned. Base and alias devices are defined to the host OS using a combination of
HCD/IODF/IOCDS. Base devices are defined by the storage system when the mainframe emulated
volumes are defined and installed.
Alias devices are created and installed with the Remote Web Console panels.
Parallel Access Volumes modes
Parallel Access Volumes operations may be performed in one of two standard operational modes.
When the P9500 is operating in IBM 2105 control unit emulation, Dynamic or Static PAV mode
can be used. When the P9500 is operating in IBM 2107 control unit emulation, Dynamic, Static
Parallel Access Volumes, or Hyper Parallel Access Volumes modes can be used.
The Parallel Access Volumes mode is controlled by the Dynamic alias management parameter
setting for the IBM Workload Manager (WLM) and the WLMPAV parameter setting in the HCD
file.
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