Migrating cyrus imap 32 to 64bit, mboxkey_db vs. mboxlist_db

[Дилян Палаузов]

Hello,

since we discuss now 64bit issues.

I have a cyrus imap 2.3.16 32bit installation, which I want to move to 
64bits (and then upgrade).

Is the right way to switch all databases to flat format, upgrade (and 
then switch back to the defaults)?

imapd.conf.5 says there are two mbox-databases: mboxkey_db and 
mboxlist_db, however 
http://cyrusimap.web.cmu.edu/docs/cyrus-imapd/2.3.16/internal/database-formats.php 
speaks only about the Mailbox List Database (mailboxes.db).  What is the 
difference between mboxkey_db and mboxlist_db?

These are the database formats (backends):  berkeley, berkeley-nosync, 
berkeley-hash, berkeley-hash-nosync, flat, skiplist, quotalegacy.

Which database formats do I have to convert from 32bit to 64bit, in 
order to achieve smooth migration?

Thanks in advance for your answer
   Dilyan