Oracle Solaris Tunable Parameters Reference Manual

shmsys:shminfo_shmmax (Solaris 9 Releases)

Obsolete in the Solaris 10 release.


Maximum size of system V shared memory segment that can be created. This parameter is an upper limit that is checked before the application sees if it actually has the physical resources to create the requested memory segment.

Attempts to create a shared memory section whose size is zero or whose size is larger than the specified value will fail with an EINVAL error.

This parameter specifies only the largest value the operating system can accept for the size of a shared memory segment. Whether the segment can be created depends entirely on the amount of swap space available on the system and, for a 32-bit process, whether there is enough space available in the process's address space for the segment to be attached.

Data Type

Unsigned long




0 - MAXUINT32 on 32-bit systems, 0 – MAXUINT64 on 64-bit systems




No. Loaded into shmmax field of shminfo structure.



When to Change

When the default value is too low. Generally changed at the recommendation of software vendors, but unless the size of a shared memory segment needs to be constrained, setting this parameter to the maximum possible value has no side effects.

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