How do I increase the number of locks in Red Hat Directory Server or Identity Management

Issue

• The following messages are logged to /var/log/dirsrv/slapd-<instance>/errors:

[21/Oct/2014:17:07:46 +0100] - libdb: Lock table is out of available lock entries

• The following messages are logged to /var/log/dirsrv/slapd-<instance>/errors:

[05/Aug/2016:00:26:46 +051800] - libdb: BDB2055 Lock table is out of available lock entries
[05/Aug/2016:00:26:46 +051800] - compactdb: failed to compact changelog; db error - 12 Cannot allocate memory

• According to Chapter 4. Tuning the Number of Locks of the Red Hat Directory Server Performance Tuning Guide I need to increase the value of nsslapd-db-locks attribute in the cn=config,cn=ldbm database,cn=plugins,cn=config entry.

• Trying to do so leads to the following error message:

# cat /root/nsslapd-db-locks.ldif 
dn: cn=config,cn=ldbm database,cn=plugins,cn=config
changetype: modify
replace: nsslapd-db-locks
nsslapd-db-locks: 20000
#
# ldapmodify -H ldap://localhost -x -D cn=directory\ manager -W  -f /root/nsslapd-db-locks.ldif 
Enter LDAP Password: 
modifying entry "cn=config,cn=ldbm database,cn=plugins,cn=config"
ldap_modify: Server is unwilling to perform (53)
    additional info: nsslapd-db-locks can't be modified while the server is running.

• How can I increase the number of locks?