			Archive Handler

Introduction

     AR (ARchive) is a pseudo-device under the RT11 operating 
system.  It allows the user to partition a large disk into many 
smaller, logical devices.  This is extremely useful if you wish
to maintain multiple files with the same name on the disk, e.g.
accounting programs you are modifying for several firms.  It
also allows temporary files to be 'hidden' on the AR device, 
rather than filling the large disk's directory.

     This device 'attaches' to a file on the large disk, and
after this attachment, the file appears to be a device to
RT11 and therefore to your programs.  Any arbitrary number of
archive files may exist on the disk, but the handler may be
attached to only eight at a time (AR0:-AR7:).  However,
multiple copies of the handler may be created to use more than
eight archive files at once.  Most valid RT11 commands
(except BOOT) will work on an ARchive file.


Instructions for use.

1)   Since the file you generate may be of any size (minimum
	of 20 blocks), DUP must be patched to ask the handler the
	size of the file.  This patch is described in the Release
	Notes for RT11, page 4-6, and is reproduced below and
	in the DUP.COM file on the disk.     

	.R SIPP
	*DUP.SAV
	Segment? 1
	Base	 30     (See patch 11.2.2)
	Offset?	 10223

	Segment	  Base	   Offset	Old	New?
	000001	  000030   010223	000	300
	000001	  000030   010224	000	^Y
	*^C
	.	

     DEC recommends starting user devices at 377. 300 was chosen to
	avoid conflicts with other user devices already installed.
	The handler may	be patched to change this allocation.

2)   Generate all ARchive files using the CREATE command from
	RT11.  Use the /ALLOCATE:xxx switch to select the size.
	Remember that several blocks will be used for the directory
	within the file (depending on the size selected), and you 
	lose seven blocks per file that normally would contain the 
	bootstrap and ID blocks.  The default extension is .ARC,
	but any RT11 name or extension is acceptable.

     You may also use the COPY/DEVICE/FILE to generate an image
	of another device (e.g. floppy disk) on your hard disk.


3)   LOAD both the AR handler, as well as the handler for the 
	real device on which the file resides, e.g.,

	LOAD AR
	LOAD RK

4)    Run the ARCDEF.SAV program to connect a particular file to
	the AR handler.  The format is  'file'=ARn:.  For example:

	a) 	PASCAL=AR0:
	b)	BASIC.GME=AR3:
	c)	SMITH.ARC=AR7:
	d)	JONES=AR3:	{Redefines AR3 so it is connected
				to the new file JONES.ARC.}

5)    Initialize the files by doing an INIT/NOQ ARn:
	DUP will use its table to determine the number of directory
	segments to allocate, or the /SEGMENTS:n command may be used.

6)    You may now copy files, assign logical names, etc. to the
	archive device.
	
	ASSIGN AR0 DK
	ASSIGN AR3 TMP
	COPY RK0:*.TMP AR3:*.*


7)    If the system is rebooted or the device on which the files
	reside is SQUEEZEd, the FILES MUST BE REDEFINED.  The
	easiest way to use this system is to place your standard
	definitions in the START%.COM file, or in a separate
	COM file for a particular application.

8)    As mentioned above, it is possible to create multiple archive
	handlers to use more than eight archives at once.  Simply
	make a copy of AR.MAC, changing only its device number.
	Assemble as before and insert the new device number into
	DUP just after the previous one.  It is suggested that new
	handlers be named AS, AT, AU, etc., with device numbers
	301, 302, 303, and so on.  ARCDEF may be used unchanged
	with any archive handler.




Restrictions.

1)	This software is provided AS IS.  No warranty is given
	concerning correct operation under all conditions.
	Berez Associates is not responsible for loss of files
	or any damages resulting from use of this software.

2)	You will note from the above descriptions that you may 
	have large areas of free storage within the files that 
	is not available to RT11.  This may be quite wasteful
	on your system.  You also lose the seven blocks per file 
	for the boot area.
3)	This software has been used on RT11 version 4 without difficulty.
	It has not been tested on earlier versions.

4)	AR functions as expected on TSX V10A.  You will note that very
	BAD results may occur if someone redefines the archive files
	while you have channels open to them.  A simple protection is
	to make ARCDEF.SAV a privileged program, i.e. rename it to 
	ARCDEF.TSX.

5)	AR does not function on TSX+ version 1.5, but appears to
	function well on TSX+ version 2.0, with the above restriction.
	You may restrict access to ARn, without allowing access to
	the large device on which the file resides. It has had 
	extensive use under this system.

6)	This is an early version of this software.  In the near future
	the handler will be modified to include the name of the file
	to which each AR device is attached.  ARCDEF will then be modified
	to provide a list of attached devices and their associated
	files.	
	Until this modification is made, the INIT/VOLUMEID command may 
	be used to place the file name in the volume ID area, and then 
	use DIR/VOLUMEID:ONLY ARn: to find the name of the attached file.

RT-11 and DECUS are trademarks of Digital Equipment Corporation
TSX and TSX+ are trademarks of S&H Computer, Nashville TN
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