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	Purger Documentation

	R. E. Gorin
	June 7, 1972


	The purger program is used to  enforce  management  decisions
that define the valid users and their disk quotas.

	The purger counts the size  of each user's files.  This  also
includes files on  [2,2] that belong  to the user,  such as mail  and
plan files.  If a user is  known to the system management then  there
will be a disk quota associated with that user.  Unknown users have a
disk quota of zero.

	If  a user is over his allocation then the purger will select
files to delete.

	A user's disk quota is expressed in "allocation units" (A.U.)
each one  of which  corresponds to  1000 (decimal)  words.  (An  A.U.
should not be confused with the  term "K" which typically means  1024
(decimal) throughout the system.)

	An  authorized  user  who  is  over his quota can specify the
purge order for his files.  This specification is accomplished  by  a
line  in  the  file OPTION.TXT on any of the user's areas.   The line
that the purger reads is called the "purge line." Only one purge line
is  allowed  for  each  user. The purger will read each of the user's
OPTION.TXT files (since there may be one for each of his disk  areas)
until  it finds one with a purge line. (Note that if two option files
have purge lines only one of these will be seen. The order  in  which
option files are read is undefined.)

	The   "purge   line"  has  the  following  format.   In  this
description curly brackets "{" and "}" denote optional items.  Pointy
brackets  "<"  and  ">" denote syntactic quantities which are defined
below. The asterisk that appears below is the Kleene star.

<Purge Line>	→	PURGE: <term>{,<term>}*;
<term> 		→	{<purge order>,}{<proj>}<file spec>
<file spec>	→	<name>{.<name>}{<proj>}
<proj>		→	[<name>]
<purge order>	→	#<number>

<number>	→	'string of decimal digits'
<name>		→	'string of alpha-numeric characters' |
			↓'string of sixbit characters'↓  |
			*

strings above that  are enclosed  in single  quotes are  meant to  be
informal definitions of the data required.

Semantics applying to the purge line.

	Each of a user's files is assigned a number, the purge order,
that determines the order  of file deletion.  The purge line  defines
the purge order of every one of a user's files.

	Every <term> in the purge  line has a purge order  associated
with it. A term that does not explicitly specify a <purge order> will
have a purge order  that is one  greater than the  term to its  left.
The first term on the line (the leftmost) will have purge order =  1,
unless that is over-ridden by an  explicit purge order.  If a  <purge
order> term is seen then that purge order will be associated with the
next term.  Subsequent terms will  be given consecutive purge  orders
unless reset by another <purge order>.

	If [<proj>] appears at the front of a term,  then  that  term
and  all subsequent terms will apply to that project area until reset
by another such term.


	The terms are then  sorted  in  order  of  their  "degree  of
specification." The "degree of specification" is defined as follows:

	Term 		degree of specification

	nnnnnn.eee[ppp]		1		most specific
	nnnnnn.*  [ppp]		2
	*     .eee[ppp]		3
	*     .*  [ppp]		4
	nnnnnn.eee[*]		5
	nnnnnn.*  [*]		6
	*     .eee[*]		7
	*     .*  [*]		8		least specific

	The most  specific  terms  are  processed  first.   Any  file
matched by a term, and not matched by a more specific term, is  given
that term's purge  order.  When  all terms are  exhausted, any  files
that have not been  matched are given a  purge order that is  greater
than any purge order used thus far.

	Files are deleted in increasing purge order until the user is
under allocation.   The purger  will not  delete any  files on  [2,2]
belonging to the user even though  it counts them against the  user's
allocation.  If the last file deleted is large, the user may wind  up
way under allocation.  This is not  a malfunction in the purger,  but
rather in the user.

	A purge may create  a DART P-dump of  all deleted files.   If
this is the case,  a file that  is a candidate  for purging need  not
have ever been dumped  before.  Otherwise, no  files belonging to  an
authorized user will be deleted unless they have been P-dumped or are
marked dump never.  EXCEPT RPG  and TMP files are deleted  regardless
of their dump status.



	If no  purge  line is  found  in  any option  file  then  the
following default line will be used:

PURGE:*.TMP,*.TEM,*.RPG,*.LST,*.REL,*.BIN,*.DMP,*.LAP,*.XGP;

NOTE:	  If the purge line in  an OPTION.TXT file does  not
	  completely specify  the  purge order  of  ALL  the
	  user's files, then the remaining files will all be
	  given the SAME purge  order.  The purger will  NOT
	  automatically apply  the default  purge orders  to
	  the remaining files.  It is up to the user to have
	  a complete purge  line.  The  default purge  order
	  applys only when there is  NO purge line given  in
	  an OPTION.TXT file.


	The OPTION.TXT file may be in E or SOS format or may be  bare
text.


Example:

PURGE:	FOO.*,GARPLY.REL[S],*.REL,*.RPG,*.TMP,*.*,FOO.BAZ,GARPLY.*,*.*[s];
This example is fairly complex.  
	Term		Purge order		Specification
	FOO.*		1			6
	GARPLY.REL[S]	2			1
	*.REL		3			7
	*.RPG		4			7
	*.TMP		5			7
	*.*		6			8
	FOO.BAZ		7			5
	GARPLY.*	8			6
	*.*[s]		9			4

Files will be purged in the following order:
	1.	FOO.*[*], except see 7 and 9 below.
	2.	Garply.rel[s] 
	3,4,5	*.rel,*.rpg,*.tmp (except see 8 below)
	6	any other files, except see below
	7	Foo.baz[*]
	8	Garply.*[*]
	9	*.*[s]

	foo.* will not delete foo.baz[*], or foo.*[s]
	Garply.rel[s] will be not be given order 8 or 9 because
		it is more specific.
	rel, rpg and tmp files will not be deleted from [s] until 9.
	Any files not described by 7,8,9 will be deleted by 6.