While starting "ldap" we had the following error. we restored the bdb_db_open file from backup and startd the service successfully.

[root@ldap]# /etc/rc.d/init.d/ldap start
Checking configuration files for slapd: bdb_db_open: unclean shutdown detected; attempting recovery.
bdb_db_open: Recovery skipped in read-only mode. Run manual recovery if errors are encountered.
bdb(dc=unibail-rodamco,dc=net): PANIC: fatal region error detected; run recovery
bdb_db_open: Database cannot be opened, err -30974. Restore from backup!
bdb(dc=unibail-rodamco,dc=net): DB_ENV->lock_id_free interface requires an environment configured for the locking subsystem
backend_startup_one: bi_db_open failed! (-30974)
slap_startup failed (test would succeed using the -u switch)
[FAILED]
stale lock files may be present in /var/lib/ldap [WARNING]


My problem is the "bdb_db_open" file is getting corrupted often 3 or 4 time in a month. What might be the problem ? Please shed your lights on this issue.