dovecot - Feb 2008 - 1.1rc1 "Transaction rolled back"?

>From my logs:
Feb 27 08:10:33 postamt dovecot: IMAP(username): expunge: uid=2793, box=Trash,
msgid=<E2FEA6DFF2340C438369E79466FB7E94F43547 at EXCHANGE01.charite.de>,
size=3025
Feb 27 08:10:33 postamt dovecot: IMAP(username): expunge: uid=2794, box=Trash,
msgid=<20080226140752B6F6EC3EF7$08D09877C3 at REALTIMEPCR>, size=12833
Feb 27 08:10:33 postamt dovecot: IMAP(username): expunge: uid=2795, box=Trash,
msgid=<8f63285b4b444b9839c94615c28bcd3347c46aec at origene.com>,
size=20931
Feb 27 08:10:33 postamt dovecot: IMAP(username): expunge: uid=2796, box=Trash,
msgid=<0118578B.8438D393 at xms1-1.vtrnz.com>, size=12066
Feb 27 08:10:33 postamt dovecot: IMAP(username): expunge: uid=2797, box=Trash,
msgid=<1204067704.28W488X7.30077 at biologyproject.net>, size=3328
Feb 27 08:10:33 postamt dovecot: IMAP(username): expunge: uid=2798, box=Trash,
msgid=<2a989b59b24e90a1f0fea02e3582ef6d at ionchannels.org>, size=10197
Feb 27 08:10:33 postamt dovecot: IMAP(username): expunge: uid=2799, box=Trash,
msgid=<20080226183239684063.12829 at mailmanager.icebase.net>, size=37658
Feb 27 08:10:33 postamt dovecot: IMAP(username): expunge: uid=2800, box=Trash,
msgid=<200802271434.GKTB5350 at monthly.smtp.com>, size=3717
Feb 27 08:10:33 postamt dovecot: IMAP(username): Transaction rolled back: Ignore
last 8 changes
Feb 27 08:10:33 postamt dovecot: IMAP(username): Disconnected: Too many invalid
IMAP commands. bytes=16371917/34458424

a) What's "Transaction rolled back"? When does it happen? What
does it
   do? Does it - in this case - UNDO the 8 expunges?
b) What's "Too many invalid IMAP commands"?
   And when ist it being triggered?
   
-- 
Ralf Hildebrandt (Ralf.Hildebrandt at charite.de)          snickebo at
charite.de
Postfix - Einrichtung, Betrieb und Wartung       Tel. +49 (0)30-450 570-155
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On Wed, 2008-02-27 at 11:08 +0100, Ralf Hildebrandt
wrote:
> Feb 27 08:10:33 postamt dovecot: IMAP(username): expunge: uid=2793,
box=Trash, msgid=<E2FEA6DFF2340C438369E79466FB7E94F43547 at
EXCHANGE01.charite.de>, size=3025
> Feb 27 08:10:33 postamt dovecot: IMAP(username): expunge: uid=2794,
box=Trash, msgid=<20080226140752B6F6EC3EF7$08D09877C3 at REALTIMEPCR>,
size=12833
> Feb 27 08:10:33 postamt dovecot: IMAP(username): expunge: uid=2795,
box=Trash, msgid=<8f63285b4b444b9839c94615c28bcd3347c46aec at
origene.com>, size=20931
> Feb 27 08:10:33 postamt dovecot: IMAP(username): expunge: uid=2796,
box=Trash, msgid=<0118578B.8438D393 at xms1-1.vtrnz.com>, size=12066
> Feb 27 08:10:33 postamt dovecot: IMAP(username): expunge: uid=2797,
box=Trash, msgid=<1204067704.28W488X7.30077 at biologyproject.net>,
size=3328
> Feb 27 08:10:33 postamt dovecot: IMAP(username): expunge: uid=2798,
box=Trash, msgid=<2a989b59b24e90a1f0fea02e3582ef6d at ionchannels.org>,
size=10197
> Feb 27 08:10:33 postamt dovecot: IMAP(username): expunge: uid=2799,
box=Trash, msgid=<20080226183239684063.12829 at mailmanager.icebase.net>,
size=37658
> Feb 27 08:10:33 postamt dovecot: IMAP(username): expunge: uid=2800,
box=Trash, msgid=<200802271434.GKTB5350 at monthly.smtp.com>, size=3717
> Feb 27 08:10:33 postamt dovecot: IMAP(username): Transaction rolled back:
Ignore last 8 changes
> Feb 27 08:10:33 postamt dovecot: IMAP(username): Disconnected: Too many
invalid IMAP commands. bytes=16371917/34458424
> 
> a) What's "Transaction rolled back"? When does it happen?
What does it
>    do? Does it - in this case - UNDO the 8 expunges?
mail_log plugin logs these messages while messages are being marked as
expunged, but all this is still done in memory. Only after transactions
are committed the expunges are really committed to disk. So the above
means that the transaction was rollbacked for some reason and no
expunging was done after all.

Transaction rollbacking doesn't happen normally though, so it should
have also logged some error. At least I can't really think of why else
it would do this.. Any idea how to reproduce it?
> b) What's "Too many invalid IMAP commands"?
>    And when ist it being triggered?
When a client sends 20 invalid commands in row. I think this is usually
related to APPENDs, but I can't really say anything about this before
seeing rawlogs..
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