Slapd hang

Hi, nearly every 2 weeks the slapd stops answering on search requests. The process is still running(socket is open as well) but every questions runs into a timeout. When that happen, I need to kill the process with "-9" manually. After that I can start the process again. We have configured a Master(Read-Write)-Slave(Read-Only) cluster, actually it happend on the Slave but it also had happend on the Master, but not that often. When the process on the Master crashes, the DB is broken and I need to restore a backup via slapcat ... Objects stored in the BDB: 40.000 Search-Requests on Slave: 3.000.000 per day Search-Requests on Master: 100.000 per day Virtualized on VMWare 5.0 Master: Debian 6 Slave: Happend on Debian 6 as well as on Debian7(now) root@ldap085:/var/openldapdb07# slapd -V @(#) $OpenLDAP: slapd (Apr 23 2013 12:16:04) $ root@lupin:/tmp/buildd/openldap-2.4.31/debian/build/servers/slapd root@ldap085:/var/openldapdb07# uname -r 3.2.0-4-amd64 Regards Carsten