Start/notes.ini Parameters/ConstrainedSHMSizeMB

ConstrainedSHMSizeMB

Parameter: ConstrainedSHMSizeMB
Short description: Limits the maximum size of the Domino server's shared memory segment in megabytes.

Profile

Parameter
ConstrainedSHMSizeMB
Category
Performance / Memory
Component
Server
Available since
9.0.1
Supported versions
9.0.1, 10.0, 11.0, 12.0, 14.0, 14.5, 14.5.1
GUI equivalent
notes.ini only (no GUI)
Possible values
Integer in MB; 0 or not set = no artificial limit

Description

ConstrainedSHMSizeMB sets an artificial upper limit for the size of the shared memory segment that the Domino server uses internally. Among other things, this segment contains the NSF buffer pool, view structures, and other server-wide data structures.
The parameter is particularly relevant when several services on a host compete for main memory, or when historical 32-bit limits must be observed. On modern 64-bit servers it primarily serves as protection against pathological memory growth (e.g. due to faulty applications or load spikes).
A value of 0 or omitting the parameter leaves sizing to the server itself.

Example configuration

ConstrainedSHMSizeMB=4096

Notes & pitfalls

  • Takes effect only after a server restart.
  • Values that are too small can prevent the server from starting or lead to out-of-memory aborts under load — check usage beforehand via show memory and show stat Mem.*.
  • Should be larger than the sum of NSF_Buffer_Pool_Size_MB, view cache, and other server structures.
  • Applies independently of the OS-side limit (e.g. vm.overcommit_memory on Linux), but can be additionally restricted by it.
  • With active DAOS and large mail servers, choose the value conservatively to leave reserves for peak loads.

Sources (HCL Product Documentation)