One of my ipa server's database had issue and left many log entries like the following in messages and slapd errors log: 

Sep 16 08:34:28 ipa0 ns-slapd: [16/Sep/2021:08:34:28.886632992 -0700] - ERR - libdb - BDB0060 PANIC: fatal region error detected; run recovery

Sep 16 08:34:29 ipa0 ns-slapd: [16/Sep/2021:08:34:28.987593487 -0700] - ERR - libdb - BDB0060 PANIC: fatal region error detected; run recovery

Sep 16 08:34:29 ipa0 ns-slapd: [16/Sep/2021:08:34:29.035181321 -0700] - ERR - libdb - BDB0060 PANIC: fatal region error detected; run recovery

Restart ipa fixed the issue. I googled for root cause and found the verified solution - https://access.redhat.com/solutions/3098131, which is to increase nsslapd-dncachememsize to a reasonable value (>150MB). This sounds like easy, however, all slapd cache parameters are related. Red Hat Directory Server performance tuning guide explain a bit: 

However, I wonder if there is a better guide. 

Thanks. 

Kathy.