Attribute 

nsslapd-listenhost on dn: cn=config

Sets the hostname for the IP interface on which Directory Server listens. This attribute is multivalued. 

You set this attribute with the ldapmodify command.

Default behavior is to listen on all interfaces. The default behavior is adapted for high volume deployments using redundant network interfaces for availability and throughput. 

Consider setting this value when deploying on a multihomed system, or when listening only for IPv4 or IPv6 traffic on a system supporting each protocol through a separate interface. Consider setting nsslapd-securelistenhost when using SSL.

Server property 

file-descriptor-count

Sets the maximum number of file descriptors Directory Server attempts to use. 

You set this server property with the dsconf set-server-prop command.

The default value is the maximum number of file descriptors allowed for a process on the system at the time when the Directory Server instance is created. The maximum value corresponds to the maximum number of file descriptors allowed for a process on the system. Refer to your operating system documentation for details. 

Directory Server uses file descriptors to handle client connections, and to maintain files internally. If the error log indicates Directory Server sometimes stops listening for new connections because not enough file descriptors are available, increasing the value of this attribute may increase the number of client connections Directory Server can handle simultaneously. 

If you have increased the number of file descriptors available on the system, set the value of this attribute accordingly. The value of this property should be less than or equal to the maximum number of file descriptors available on the system. 

Attribute 

nsslapd-nagle on dn: cn=config

Sets whether to delay sending of TCP packets at the socket level. 

You set this attribute with the ldapmodify command.

Consider setting this to on if you need to reduce network traffic.

Attribute 

nsslapd-reservedescriptors on dn: cn=config

Sets the number of file descriptors Directory Server maintains to manage indexing, replication and other internal processing. Such file descriptors become unavailable to handle client connections.

You set this attribute with the ldapmodify command.

Consider increasing the value of this attribute from the default of 64 if all of the following are true.

• Directory Server replicates to more than 10 consumers or Directory Server maintains more than 30 index files.

• Directory Server handles a large number of client connections.

• Messages in the error log suggest Directory Server is running out of file descriptors for operations not related to client connections.

Notice that as the number of reserved file descriptors increases, the number of file descriptors available to handle client connections decreases. If you increase the value of this attribute, consider increasing the number of file descriptors available on the system, and increasing the value of file-descriptor-count.

If you decide to change this attribute, for a first estimate of the number of file descriptors to reserve, try setting the value of nsslapd-reservedescriptors according to the following formula.

20 + 
4 * (number of databases) +
 (total number of indexes) + 
(value of nsoperationconnectionslimit) * 
(number of chaining backends) + 
ReplDescriptors + 
PTADescriptors + 
SSLDescriptors

Here ReplDescriptors is number of supplier replica plus 8 if replication is used. PTADescriptors is 3 if the Pass Through Authentication, PTA, plug-in is enabled, and 0 otherwise. SSLDescriptors is 5 if SSL is used, and 0 otherwise.

The number of databases is the same as the number of suffixes for the instance, unless the instance is configured to use more than one database per suffix. Verify estimates through empirical testing. 

Attribute 

nsslapd-securelistenhost on dn: cn=config

Sets the hostname for the IP interface on which Directory Server listens for SSL connections. This attribute is multivalued. 

You set this attribute with the ldapmodify command.

Default behavior is to listen on all interfaces. Consider this attribute in the same way as nsslapd-listenhost.

Server property 

max-thread-count

Sets the number of threads Directory Server uses. 

You set this server property with the dsconf set-server-prop command.

Consider adjusting the value of this property if any of the following are true.

• Client applications perform many simultaneous, time-consuming operations such as updates or complex searches.

• Directory Server supports many simultaneous client connections.

Multiprocessor systems can sustain larger thread pools than single processor systems. As a first estimate when optimizing the value of this attribute, use two times the number of processors or 20 plus the number of simultaneous updates. 

Consider also adjusting the maximum number of threads per client connection, max-threads-per-connection-count. The maximum number of these threads handling client connections cannot exceed the maximum number of file descriptors available on the system. In some cases, it may prove useful to reduce, rather than increase, the value of this attribute.

Verify estimates through empirical testing. Results depend not only on the particular deployment situation but also on the underlying system.