Subject: major change in new BETA version of UW IMAP toolkit

From: Mark Crispin <[email-masked]>
Date: Fri, 25 Jun 1999 13:21:58 -0700 (PDT)

The latest version of the IMAP-4.6.BETA toolkit
	ftp://ftp.cac.washington.edu/mail/imap-4.6.BETA.tar.Z
contains a new rewrite algorithm for the default UNIX format of mail.  
This algorithm is *DISABLED* by default in this distribution, but will be
enabled in the future.

The new algorithm is much faster than the current algorithm, and does not
require a tmpfile.  However, the new algorithm is much more dangerous than
the old algorithm since it reads and overwrites on the mail file
simultaneously.  Any bug in the algorithm is likely to cause mail file
corruption.

The new algorithm has been tested and debugged here at UW.  There are no
known bugs in the new algorithm.  However, it has not yet received
extensive loadtesting in the field.  I want people to try it, but it is
probably not prudent to put it into production without testing at your
site.

Please test the new algorithm (preferably on mailboxes which you have
backed up), and let us know if you encounter any problems.

To enable the new algorithm, edit file
	imap-4.6.BETA/src/osdep/unix/unix.c
and look for a line that reads:

int unix_old_algorithm = T;	* non-zero to use old algorithm */

Change that line to be:

int unix_old_algorithm = NIL;	/* non-zero to use old algorithm */

If you do not make this change, you will get the old slow algorithm that
is in previous versions.  Note, however, that the old algorithm will be
retired soon, so you probably should test the new algorithm.

This change does not affect any other drivers (e.g. mbx).

-- 
-----------------------------------------------------------------
 For information about this mailing list, and its archives, see: 
 http://www.washington.edu/imap/imap-list.html
-----------------------------------------------------------------

---

From: Lai Yiu Fai <[email-masked]>
Date: Mon, 28 Jun 1999 11:20:37 +0800

How is it compared with the mbx format?  MBX seems to be UW recommended format
in previous release.   How about concurrent RW and purging support in new 
unix driver?  Is it still not supported?

Rgds,
Ken

---

From: Mark Crispin <[email-masked]>
Date: Sun, 27 Jun 1999 22:20:11 -0700 (PDT)

On Mon, 28 Jun 1999 11:20:37 +0800, Lai Yiu Fai wrote:
> How is it compared with the mbx format?  MBX seems to be UW recommended
> format in previous release.   How about concurrent RW and purging support in
> new unix driver?  Is it still not supported?

mbx format is still faster than the default unix format, even with the new
faster unix format algorithm; and this will always be the case.  However, the
difference is no longer as great as with the old algorithm.

Concurrent RW and expunge support is still not supported in the default unix
format.  It is difficult to do this, due to the locking requirements imposed
on the default unix format by other software.  Also, there are still some
issues having to do with message relocation due to flag changes.  mbx format
is not hampered by either of these issues.