Problem with cyrus 2.3.16-6, sendmail, saslauthd on centos 6

Hi,
we have installed a cyrus-imapd server on a centos 6.6 architecture.
Unfortunatly our service has some bugs:

1. we stop the service, process cyrus files remain in /var/lib/imap/proc
2. we have many errors in /var/log/maillog

--------------------------------------------------------------------------
Mar 29 15:53:00 mailbox lmtpunix[20870]: DBERROR db4: Logging region out
of memory; you may need to increase its
  size
Mar 29 15:53:00 mailbox lmtpunix[20870]: DBERROR:
opening /var/lib/imap/deliver.db: Cannot allocate memory
Mar 29 15:53:00 mailbox lmtpunix[20870]: DBERROR:
opening /var/lib/imap/deliver.db: cyrusdb error
Mar 29 15:53:00 mailbox lmtpunix[20870]: FATAL: lmtpd: unable to init
duplicate delivery database
Mar 29 15:53:00 mailbox master[27585]: process 20870 exited, status 75
Mar 29 15:53:00 mailbox master[27585]: service lmtpunix pid 20870 in
READY state: terminated abnormally
Mar 29 15:53:00 mailbox master[20871]: about to
exec /usr/lib/cyrus-imapd/lmtpd
Mar 29 15:53:00 mailbox lmtpunix[20871]: executed
Mar 29 15:53:00 mailbox lmtpunix[20871]: DBERROR db4: Logging region out
of memory; you may need to increase its
  size
---------------------------------------------------------------------------

We setup a cyrus db configuration /var/lib/imap/db/DB_CONFIG in this
way:
set_cachesize 0 2097152 1
set_lg_regionmax 1048576

but the problem is always present.

Please can you help us?
Thank a lot in advance.

Regards
D. Bortolotti & A. Monducci