Start/notes.ini Parameters/Server_MaxSessions

Server_MaxSessions

Parameter: Server_MaxSessions
Short description: Limits the maximum number of concurrent NRPC sessions on a Domino server. Default: 65535 (effectively unlimited). A manual limit forces the server to drop sessions idle for more than 1 minute before accepting new ones — a typical protection / recycling setting.

Profile

Parameter
Server_MaxSessions
Category
Performance / server access
Component
Server (NRPC listener)
Available since
8.5
Supported versions
9.0.1, 10.0, 11.0, 12.0, 14.0, 14.5, 14.5.1
GUI equivalent
notes.ini only, but can also be maintained in the Configuration document under NOTES.INI Settings.
Possible values
Integer ≥ 1. Default: 65535 (internally “unlimited”, equals MaxDbServerTasks). Typical manual values: 1000–10000.

Description

An NRPC session is the bracket in which a Notes client (or another server) groups its database operations against the Domino server. Per logged-in user, typically 1 to several sessions are created, depending on the Notes-client behavior (workspace, mail replicas, third-party add-ons).
Server_MaxSessions defines the hard upper bound for concurrent NRPC sessions. Once the limit is reached, the server starts to drop idle sessions (more than 1 minute inactive) before accepting new sessions. If the limit is not reached, Domino does not recycle sessions.
When to set?
  • Overload protection: on servers with unclear peak load, define a hard upper bound instead of relying on the default 65535.
  • With increased Replicators or MailMaxThreads: HCL recommends lowering Server_MaxSessions when raising parallel replicators / routers — otherwise the additional tasks accumulate and threaten to overload the server.
  • Memory pressure: every active session holds server memory (session structures, open NSF handles, cache entries). A limit reduces the worst-case consumption.
Related limits:
  • Server_MaxUsers — limits the number of distinct user names, not sessions.
  • Server_Session_Timeout — inactivity timeout in minutes, after which a session is ended by the server.
  • Server_Pool_Tasks — limits the number of worker threads per Notes port, not sessions.

Example configuration

Classic protection limit:
Server_MaxSessions=5000
Combined with a moderate session timeout:
Server_MaxSessions=5000
Server_Session_Timeout=240
Remove the limit / restore the default:
set config Server_MaxSessions=

Notes & pitfalls

  • “Sessions” ≠ “users”: a user can hold multiple sessions (workspace, mail, local replicas via the same server). A Server_MaxSessions limit that is too small therefore hits well below the number of users.
  • Default is effectively unlimited: 65535 is never reached in practice; without an explicit limit, the parameter has no effect.
  • Performance effect: only takes effect when the limit is reached. Below the limit there is no behavior change.
  • Interaction: anyone enabling parallel Replicators / more MailMaxThreads should possibly lower Server_MaxSessions to cap the overall load.
  • Change takes effect immediately via set config Server_MaxSessions=… — no server restart required.
  • Monitoring: show stat Server.Sessions.*, show users, show server — including drop statistics.
  • Security aspect: in case of suspected DoS (very many short-lived connections), Server_MaxSessions is an important hardening switch.
  • Works on all supported platforms.

Sources (HCL Product Documentation)

  • HCL Support Knowledge Base KB0033353 – Calculating Server_MaxSessions