Technical data

System Dump Analyzer
SHOW DEVICE
Symbol Meaning
ORB Address of object rights block
DDB Address of device data block
DDT Address of driver dispatch table
CRB Address of channel request block
AMB Associated mailbox UCB pointer
IRP Address of I/O request packet
2P_UCB Address of alternate UCB for dual-pathed device
LNM Address of logical name block for mailbox
PDT Address of port descriptor table
CDDB Address of class driver descriptor block for MSCP-served device
2P_CDDB Address of alternate CDDB for MSCP-served device
RWAITCNT Resource wait count for MSCP-served device
VCB Address of volume control block for mounted device
If you are examining a driver-related crash, you might find it helpful to issue
a SHOW STACK command after the appropriate SHOW DEVICE command,
examining the stack for any of these symbols. Note, however, that although
SHOW DEVICE defines those symbols relevant to the last device unit it has
displayed, and redefines symbols relevant to any subsequently displayed device
unit, it does not undefine symbols. (For instance, SHOW DEVICE DUA0 defines
the symbol PDT, but SHOW DEVICE MBA0: does not undefine it, even though
the PDT structure is not associated with a mailbox device.)
To maintain the accuracy of symbols that appear in the stack listing, use the
DEFINE command to modify the symbol name. For example:
SDA> DEFINE DUA0_PDT PDT
SDA> DEFINE MBA0_UCB UCB
See the descriptions of the READ and FORMAT commands for additional
information about defining and examining the contents of device data structures.
For a detailed explanation of I/O data structures displayed by SDA, consult the
OpenVMS VAX Device Support Manual.
Examples
1.
SDA>SHOW DEVICE VTA20
VTA20 ==> LTA20 VT200_Series UCB address: 8042E4C0
Device status: 00010110 online,bsy,deleteucb
Characteristics: 0C040007 rec,ccl,trm,avl,idv,odv
00000200 nnm
Owner UIC [000001,000004] Operation count 5793 ORB address 8042E590
PID 00010064 Error count 0 DDB address 80CEF2E0
Class/Type 42/6E Reference count 2 DDT address 807696FB
Def. buf. size 80 BOFF 0155 CRB address 80BC8B00
DEVDEPEND 180093A0 Byte count 0100 IRP address 80BE2B00
DEVDEPND2 7962100C SVAPTE 804801C0 I/O wait queue empty
FLCK/DLCK 00000012 DEVSTS 0000
I/O request queue
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SDA–105