Technical data

System Dump Analyzer
SHOW DEVICE
Description
The SHOW DEVICE command produces several displays taken from system data
structures that describe the devices in the system configuration.
If you use the SHOW DEVICE command to display information for more than
one device or one or more controllers, it initially produces the DDB list display
to provide a brief summary of the devices for which it renders information in
subsequent screens.
Information in the DDB list appears in six columns, the contents of which are as
follows:
• Address of the device data block (DDB)
• Controller name
• Name of the ancillary control process (ACP) or extended QIO processor (XQP)
associated with the device
• Name of the device driver
• Address of the driver prologue table (DPT)
• Size of the DPT
The SHOW DEVICE command then produces a display of information pertinent
to the device controller. This display includes information gathered from the
following structures:
• Device data block (DDB)
• Primary channel request block (CRB)
• Interrupt dispatch block (IDB)
• Driver dispatch table (DDT)
If the controller is an HSC controller, SHOW DEVICE also displays information
from its system block (SB) and each path block (PB).
Many of these structures contain pointers to other structures and driver routines.
Most notably, the DDT display points to various routines located within driver
code, such as the start I/O routine, unit initialization routine, and cancel I/O
routine.
For each device unit subject to the SHOW DEVICE command, SDA displays
information taken from its unit control block, including a list of all I/O request
packets (IRPs) in its I/O request queue. For certain mass-storage devices, SHOW
DEVICE also displays information from the primary class driver data block
(CDDB), the volume control block (VCB), and the ACP queue block (AQB). For
units that are part of a shadow set, SDA displays a summary of shadow set
membership.
As it displays information for a given device unit, SHOW DEVICE defines the
following symbols as appropriate.
Symbol Meaning
UCB Address of unit control block
SB Address of system block
SDA–104