MyISAM Too many open files; + index.cache: Cannot allocate memory

[Voytek Eymont]

installed new Dovecot 2.2 on Centos 7, and, migrated some users from old
server

# dovecot --version
2.2.33.2 (d6601f4ec)

works OK, but, noticed some sql and index.cache errors

what am I missing ?

only noticed this one so far
------------------
# grep "Too many open files"   /var/log/dovecot.log
Jan 02 15:22:16 auth-worker(1411): Warning: mysql: Query failed, retrying:
Got error 24 "Too many open files" from storage engine MyISAM
Jan 02 15:22:16 auth-worker(1411): Error:
sql(bb at tld.com.au,183.88.2.248,<VzebccNhtPO3WAL4>): User query failed: Got
error 24 "Too many open files" from storage engine MyISAM

lots of this one
----------------------------
Jan 16 09:08:36 imap(postmaster at sbt.net.au): Error: mmap(size=263578648)
failed with file
//var/vmail/vmail1/sbt.net.au/postmaster at sbt.net.au//Maildir/dovecot.index.cache:
Cannot allocate memory
Jan 16 09:08:38 imap(postmaster at sbt.net.au): Error: mmap(size=263578648)
failed with file
//var/vmail/vmail1/sbt.net.au/postmaster at sbt.net.au//Maildir/dovecot.index.cache:
Cannot allocate memory
Jan 16 09:31:23 imap(postmaster at sbt.net.au): Error: mmap(size=263578648)
failed with file
//var/vmail/vmail1/sbt.net.au/postmaster at sbt.net.au//Maildir/dovecot.index.cache:
Cannot allocate memory

MariaDB
Network traffic since startup: 3.9 GiB
This MySQL server has been running for 12 days, 3 hours, 1 minutes and 21
seconds. It started up on Jan 04, 2018 at 04:23 PM.

Traffic 	ø per hour
Received	1.2 GiB	4.2 MiB
Sent	2.7 GiB	9.5 MiB
Total	3.9 GiB	13.7 MiB
Connections	ø per hour	%
max. concurrent connections	63	---	---
Failed attempts	51	0.18	<0.01%
Aborted	809	2.78	0.07%
Total	1,166 k	4,006.43	100.00%
----------
Questions since startup: 9,850,430
ø per hour: 33,846
ø per minute: 564
ø per second: 9



-- 
Voytek