unclean shutdown detected; attempting recovery - question

[frank.offermanns@caseris.de]

Hello,

I am using OpenLDAP 2.4.25.
After reboot I see logs (Logsetting -d 256) like :
=> bdb_idl_delete_key: c_del id failed: DB_LOCK_DEADLOCK: Locker killed to 
resolve a deadlock (-30994)
I checked this and found that I can ignore this.
But one minute after this message OpenLDAP stopped working. 
I automatically detected it and restarted OpenLDAP.

After restarting I see a logmessage:
hdb_db_open: database "o=mydomain": unclean shutdown detected; attempting 
recovery.

Then I see for 1 to 3 minutes that OpenLDAP seems to work, before stopping 
the work again.
I repeated restarting.
After the sixths restarts LDAP now seems to work correctly.

So now my question:
When I see the message: "unclean shutdown detected; attempting recovery"
How long does the recovery take? Is it possbile that the recovery was 
still in progress as I restarted (after 5 mins) OpenLDAP?
Is there a Logsetting I could activate to see when the recovery is 
finished?
Would it be better to manually do the recovery after stopping slapd?

Regards,
Frank