Library /sys$common/syshlp/helplib.hlb  —  LD  New features V9.0
 	V9.0 has the following new features:

 	The major new feature is virtual tape support. This allows a file
 	on disk to be used as a tape device, which can be very handy for
 	testing. To use it substitute the LM command for LD, like this:

 	$ @sys$startup:lm$startup
 	$ lm create tape.dsk/size=10000
 	$ lm connect/log/full tape.dsk lma1:
 	%LM-I-CONNECTED, Connected $3$LMA1: to $3$DKA100:[JUR.LD.V90.SRC]TAPE.DSK;1
 	-LM-I-OPTIONS, Tape unit, Tape loaded
 	%LM-I-METADATA, Metadata available

 	Version:                 1
 	Creator:                 JUR
 	Process name:              SysDamager
 	Account:                 SYSTEM
 	UIC:                     [100,100]
 	Created on system:       THEBAT
 	VMS version:             V8.3
 	Time at creation:         8-MAY-2007 20:50:19.90
 	Time at last connect:     8-MAY-2007 20:50:25.49
 	Time at last disconnect:  8-MAY-2007 20:50:19.90
 	Data start:              1
 	Data size:               9999
 	Flags:                   tagsinuse
 	Checksum:                3A4D74B7

 	$ show dev/full lma1

 	Magtape $3$LMA1: (THEBAT), device type (Generic SCSI tape), is online, file-
     	oriented device.

 	Error count                    0    Operations completed                  2
 	Owner process                 ""    Owner UIC                         [JUR]
 	Owner process ID        00000000    Dev Prot            S:RWPL,O:RWPL,G:R,W
     	Reference count                0    Default buffer size                2048
     	Density                  default    Format                        Normal-11
     	Allocation class               3

 	  Volume status:  no-unload on dismount, odd parity.

 	$ lm trace lma1/all
 	$ init lma1 test
 	$ mount lma1 test
 	%MOUNT-I-MOUNTED, TEST mounted on _$3$LMA1: (THEBAT)
 	$ lm show/trace lma1
 	         I/O trace for device $3$LMA1:
 	     8-MAY-2007 20:51:59.14 on node THEBAT

 	End Time           Elaps    Pid       Lbn     Bytes  Iosb    Function
 	---------------------------------------------------------------------
 	20:51:49.649071 00.000005 2020042F          0      0 NORMAL  PACKACK
 	20:51:49.649133 00.000000 2020042F          0      0 NORMAL  REWIND
 	20:51:49.649174 00.000001 2020042F          0      0 NORMAL  SETMODE|MT3_DENSITY
 	20:51:49.664598 00.014676 00000000          1 131072 NORMAL  READPBLK
 	20:51:49.666553 00.001917 00000000        257 131072 NORMAL  READPBLK
 	20:51:49.676429 00.009853 00000000        513 131072 NORMAL  READPBLK
 	20:51:49.686808 00.010357 00000000        769 131072 NORMAL  READPBLK
 	20:51:49.686837 00.036922 2020042F          0     80 OPINCOMPL READPBLK
 	20:51:49.686904 00.000001 2020042F          0      0 NORMAL  REWIND
 	20:51:49.686945 00.000000 2020042F          0      0 NORMAL  SETMODE|MT3_DENSITY
 	20:51:49.687029 00.000001 2020042F          0      0 NORMAL  REWIND
 	20:51:49.687083 00.000014 2020042F          0     80 NORMAL  WRITEPBLK
 	20:51:49.687150 00.000010 2020042F          0     80 NORMAL  WRITEPBLK
 	20:51:49.687209 00.000010 2020042F          0     80 NORMAL  WRITEPBLK
 	20:51:49.687261 00.000001 2020042F          0      0 NORMAL  WRITEOF
 	20:51:49.687292 00.000001 2020042F          0      0 NORMAL  WRITEOF
 	20:51:49.687332 00.000009 2020042F          0     80 NORMAL  WRITEPBLK
 	20:51:49.687378 00.000009 2020042F          0     80 NORMAL  WRITEPBLK
 	20:51:49.687412 00.000001 2020042F          0      0 NORMAL  WRITEOF
 	20:51:49.687442 00.000001 2020042F          0      0 NORMAL  WRITEOF
 	20:51:49.692443 00.004969 00000000          1   1024 NORMAL  WRITEPBLK
 	20:51:49.692483 00.005014 2020042F          0      0 NORMAL  REWIND
 	20:51:49.692533 00.000001 2020042F          0      0 NORMAL  AVAILABLE
 	20:51:49.692586 00.000001 2020042F          0      0 NORMAL  AVAILABLE
 	20:51:53.556264 00.000003 2020042F          0      0 NORMAL  PACKACK
 	20:51:53.556314 00.000000 2020042F          0      0 NORMAL  REWIND
 	20:51:53.556357 00.000000 2020042F          0     16 NORMAL  SENSEMODE|MT3_DENSITY
 	20:51:53.556416 00.000000 2020042F          0      0 NORMAL  SETMODE|MT3_DENSITY
 	20:51:53.556471 00.000001 2020042F          0      0 NORMAL  PACKACK
 	20:51:53.556505 00.000001 2020042F          0      0 NORMAL  REWIND
 	20:51:53.568662 00.012108 00000000          1 131072 NORMAL  READPBLK
 	20:51:53.570605 00.001909 00000000        257 131072 NORMAL  READPBLK
 	20:51:53.572169 00.001541 00000000        513 131072 NORMAL  READPBLK
 	20:51:53.573773 00.001583 00000000        769 131072 NORMAL  READPBLK
 	20:51:53.573811 00.017262 2020042F          0     80 NORMAL  READPBLK
 	20:51:53.582545 00.000014 2020042F          0     80 NORMAL  READPBLK
 	20:51:53.582615 00.000009 2020042F          0     80 NORMAL  READPBLK
 	20:51:53.582667 00.000001 2020042F          0     80 ENDOFFILE READPBLK
 	20:51:53.582736 00.000001 2020042F          0      0 NORMAL  REWIND

 	There are three commands for volume switch support: LM LOAD, UNLOAD
 	and SWITCH. Initially an LM device can be created without a connected
 	containerfile, with LM CONNECT/NOLOAD LMAx.

 	After that it can be unloaded with LM UNLOAD LMAx, and reloaded
 	with LM LOAD file LMAx. Switching a volume can be done in one
 	command with LM SWITCH file LMAx. LM SHOW/FULL will display if
 	the tape is loaded or not. So right now DISMOUNT/UNLOAD (the default)
 	will keep the file connected, but move it to the unload state. It is
 	possible to reload it and keep the same file with LM LOAD LMAx (special
 	case command). If the device is unloaded it will return SS$_MEDOFL
 	when it's accessed. LM LOAD and SWITCH can use the same qualifiers
 	as CONNECT, UNLOAD can use the same qualifiers as DISCONNECT.

 	If a device is not connected to a container file it can simply be
 	removed with LM DISCONNECT LMAx.

 	  LM SWITCH newfile.dsk LMA1

 	This command allows volume switching for backup. The existing virtual
 	tapeunit is re-used with a new container file. If backup is at the end
 	of a tape and issues an Opcom request this commands allows switching of
 	the containerfile.

 	One thing to notice is that a tape containerfile must be at least 5000
 	blocks in size. The virtual end of tape is currently fixed at 95% of
 	the containerfile size, after writing that amount of data the driver
 	will return SS$_ENDOFTAPE after every write. This is a warning message
 	only, the data will be written correctly. If the physical end of data
 	is reached an SS$_DRVERR will be returned.

 	  LM ANALYZE file.dsk [/RECORDS] [/DATA]

 	This command will verify the integrity of the container file. It can
 	only be used for virtual tapes, disks have their own format (ODS-2/5).
 	The qualifier /RECORDS will show all records with their possible
 	attributes. /DATA will dump the contents of the data records in hex
 	and ascii:

 	$ lm analyze tape/records
 	%LM-I-METADATA, Metadata available

 	Version:                 1
 	Creator:                 JUR
 	Process name:              SysDamager
 	Account:                 SYSTEM
 	UIC:                     [100,100]
 	Created on system:       THEBAT
 	VMS version:             V8.3
 	Time at creation:         8-MAY-2007 20:50:19.90
 	Time at last connect:     8-MAY-2007 20:50:25.49
 	Time at last disconnect:  8-MAY-2007 20:53:23.54
 	Data start:              1
 	Data size:               9999
 	Flags:                   tagsinuse
 	Checksum:                A7C35A3F

 	Record:        0 Offset:              0 Lbn:          1 Length:       80
 	Record:        1 Offset:            116 Lbn:          1 Length:       80
 	Record:        2 Offset:            232 Lbn:          1 Length:       80
 	Record:        3 Offset:            348 Lbn:          1 Length:        0 Flags: EOF
 	Record:        4 Offset:            384 Lbn:          1 Length:        0 Flags: EOF
 	Record:        5 Offset:            420 Lbn:          1 Length:       80
 	Record:        6 Offset:            536 Lbn:          2 Length:       80
 	Record:        7 Offset:            652 Lbn:          2 Length:        0 Flags: EOF
 	Record:        8 Offset:            688 Lbn:          2 Length:        0 Flags: EOF
 	Record:        0 Offset:              0 Lbn:          1 Length:        0 Flags: EOD
 	%LM-I-ANALYZEOK, Container file structure successfully verified
 	Bytes read:           524288
 	Records read:             10
 	Databytes read:          400
 	Eof count:                 4

 	  LD CREATE/ERASE

 	This will erase the containerfile after creation. It may be used
 	to speed up initial shadow copies, or when init has a problem
 	initializing a virtual disk due to previous stale data and the
 	user lacks VOLPRO privilege to override that.

 	If creation of a containerfile is done on a disk with highwater
 	marking enabled, a warning will be issued that it may take some
 	time if the filesize is above 100000 blocks (VMS V8.2 and higher
 	only).

 	  LD CONNECT/LOGICAL=(NAME=logical-name[,TABLE=table][,MODE=mode])

 	This allows a logical name to be associated with the connected LD
 	device.

 	  LD SHOW/FULL

 	This will show all attributes of the selected LD device:

 	$ ld show/all/full
 	%LD-I-CONNECTED, Connected _$3$LDA1: to $1$DGA100:[JUR.LD.V90.SRC]FILE.DSK;1
 	-LD-I-OPTIONS, Shared
 	%LD-I-CONNECTED, Connected _$3$LDA2: to _$3$DQA0:
 	-LD-I-OPTIONS, Replaced, Trace active, No DSE support, Not Forced Error capable

 	  LD SHOW/TRACE/TIMESTAMP=START or END

 	This allows selection of absolute start and end time of trace data.

 	  LD SHOW/SYMBOL

 	This will get the LD unit number in DCL symbol LD_UNIT, and the
 	container file specification in the symbol LD_CONTAINER.
 	For tape it will be LM_UNIT and LM_CONTAINER.

 	There's more accurate timing in trace messages (microsecond accuracy)
 	(Only in VMS V8.3 and higher):

 	$ ld show/trace lda1
 	        I/O trace for device $3$LDA1:
 	17-MAY-2006 09:21:15.16 on node THEBAT

 	End Time           Elaps    Pid       Lbn     Bytes  Iosb    Function
 	---------------------------------------------------------------------
 	09:21:12.232269 00.000000 2060042F          0      0 NORMAL  PACKACK
 	09:21:12.240950 00.008581 2060042F          1    512 NORMAL  READPBLK
 	09:21:12.247513 00.006426 2060042F       1034    512 NORMAL  READPBLK
 	09:21:12.248595 00.000959 2060042F      50033    512 NORMAL  READPBLK
 	09:21:12.249557 00.000838 2060042F      50034    512 NORMAL  READPBLK
 	09:21:12.255176 00.005504 2060042F      50016    512 NORMAL  READPBLK
 	09:21:12.263548 00.008258 2060042F      50016    512 NORMAL  WRITEPBLK

 	LD SHOW/TRACE can now show the contents of the LBN and BYTECOUNT fields
 	in decimal and hex with /LBN=[HEX,DECICMAL] or /BYTECOUNT=[HEX,DECIMAL].

 	Trace data for the LM device will by default not contain the data
 	to/from disk initiated by the driver (with a PID field of 0). To
 	enable tracing of this data use /ALL with LD TRACE.

 	Known issues:

 	LM SHOW/TRACE/CONTINOUS can not yet be trusted completely, it may cause
 	invalid data to be written to tape if used together with writing to
 	tape.

 	Switching volumes due to tape full on a Files-11 mounted tape may
 	get errors.

 	The accurate timing measurements may be way off if a cpu is stopped and
 	restarted. Disconnecting and reconnecting the LD device will fix it.

 	Copying .OBJ files (and possibly others) may give SS$_BADATTRIB errors.
 	This is not stricktly an error since any copy of a file on a files-11
 	mounted tape may generate this error for records smaller than 14 bytes.
 	These small records are rejected by the VMS I/O system as documented
 	in the I/O User's reference manual. A real tape device will behave the
 	same.
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