My master Zimbra ldap-only server has stopped working each weekend for the last two weeks. I believe it is related to the full backup that is run each weekend:

Code:
0 1 * * 6 /opt/zimbra/bin/zmbackup 
0 0 * * * /opt/zimbra/bin/zmbackup -del 1m
It seems that the weekend's backup starts more than one zmslapcat which makes LDAP unresponsive to one of my store servers so that LMTP fails and users on that server cannot login (I am using multiple store servers). LDAP then won't shut down until the slapcats are each manually killed. While it is down I have no problem running a full backup with zmbackupldap which produces the same ldiff files that I find on my secondary ldap server which is syncrepl'd from the master.

I've read some of the code to trace down what I think is happending: zmbackupldap calls zmslapcat which seems to call OpenLDAP's standard slapcat command whose man page says: "slapd(8) should not be running (at least, not in read-write mode) when you do this [slapcat] to ensure consistency of the database". I don't think I see any commands to shut down ldap in zmbackupldap. I could have overlooked something.

/var/log/zimbra.log at the time of incident shows nothing out of the ordinary until I initiated a shutdown which produced many ZimbraLdapContext ServiceUnavailableException until I killed the slapcats and slapd was restarted.

Questions:

1. Does zmbackup stop Zimbra's LDAP for backups and is this relevant?

2. Is there anywhere else that I should look?