Database error 22

[Olivier Nicole <on@cs.ait.ac.th>]

Hi,

After a reboot this morning I had the error:

Jun 23 06:47:47 ldap slapd[512]: @(#) $OpenLDAP: slapd 2.3.40 (Jan 29 2008 12:27:46) $  root@fbsd35.cs.ait.ac.th:/usr/ports/net/openldap23-server/work/openldap-2.3.40/servers/slapd
Jun 23 06:47:49 ldap slapd[522]: bdb_db_open: Database cannot be opened, err 22. Restore from backup!
Jun 23 06:47:49 ldap slapd[522]: bdb(dc=cs,dc=ait,dc=ac,dc=th): DB_ENV->lock_id_free interface requires an environment configured for the locking subsystem
Jun 23 06:47:49 ldap slapd[522]: bdb(dc=cs,dc=ait,dc=ac,dc=th): txn_checkpoint interface requires an environment configured for the transaction subsystem
Jun 23 06:47:49 ldap slapd[522]: bdb_db_close: txn_checkpoint failed: Invalid argument (22)
Jun 23 06:47:49 ldap slapd[522]: backend_startup_one: bi_db_open failed! (22)
Jun 23 06:47:49 ldap slapd[522]: bdb_db_close: alock_close failed
Jun 23 06:47:49 ldap slapd[522]: slapd stopped.
Jun 23 06:47:49 ldap slapd[522]: connections_destroy: nothing to destroy.

Yesterday I think I cleanly halted the LDAP server before the UPS ran
out of battery (major power failure). This morning when I restarted
the machine I find the above error.

1) What could cause this error?

2) How to do clean and regular backups?

Best regards,

Olivier