`msgsys:msginfo_msgmax`

Description	Maximum size of System V message.
Data Type	Unsigned long
Default	2048
Range	0 to amount of physical memory
Units	Bytes
Dynamic?	No. Loaded into `msgmax` field of `msginfo` structure.
Validation	None
When to Change	When `msgsnd`(2) calls return with error of `EINVAL` or at the recommendation of a software vendor.
Commitment Level	Unstable

`msgsys:msginfo_msgmnb`

Description	Maximum number of bytes that can be on any one message queue.
Data Type	Unsigned long
Default	4096
Range	0 to amount of physical memory
Units	Bytes
Dynamic?	No. Loaded into `msgmnb` field of `msginfo` structure.
Validation	None
When to Change	When `msgsnd()` calls block or return with an error of `EGAIN`, or at the recommendation of a software vendor.
Commitment Level	Unstable

`msgsys:msginfo_msgmni`

Description	Maximum number of message queues that can be created.
Data Type	Signed integer
Default	50
Range	0 to MAXINT
Dynamic?	No. Loaded into `msgmni` field of `msginfo` structure.
Validation	None
When to Change	When `msgget`(2) calls return with an error of `ENOSPC` or at the recommendation of a software vendor.
Commitment Level	Unstable

`msgsys:msginfo_msgtql`

Description	Maximum number of messages that can be created. If a `msgsnd` call attempts to exceed this limit, the request is deferred until a message header is available. Or, if the request has set the `IPC_NOWAIT` flag, the request fails with the error `EAGAIN`.
Data Type	Signed integer
Default	40
Range	0 to MAXINT
Dynamic?	No. Loaded into `msgtql` field of `msginfo` structure.
Validation	None
When to Change	When `msgsnd()` calls block or return with error of `EGAIN`, or at the recommendation of a software vendor.
Commitment Level	Unstable

System V Semaphores

System V semaphores provide counting semaphores in the Solaris environment. In addition to the standard set and release operations for semaphores, System V semaphores can have values that are incremented and decremented as needed (for example, to represent the number of resources available). The ability is offered to do operations on a group of semaphores simultaneously as well as to have the system undo the last operation by a process if it dies.

Semaphores are created in sets.

The module is dynamically loaded on first reference. Parameters provided to the subsystem are validated at that time and all data structures (including the semaphores) are created. Values for parameters are, accordingly, not changeable at runtime because increases in values would lead to data corruption. Entries in the /etc/system file must contain the semsys: prefix.

This facility is different from the POSIX 1003.1b semaphore facility.

`semsys:seminfo_semmni`

Description	Maximum number of semaphore identifiers.
Data Type	Signed integer
Default	10
Range	1 to 65,535
Dynamic?	No
Validation	Compared to `SEMA_INDEX_MAX` (currently 65,535) and reset to that value if larger. A warning message is written to the console and or system messages file.
When to Change	When the default number of sets is not enough. Generally changed at the recommendation of software vendors. No error messages are displayed when an attempt is made to create more sets than are currently configured. The application sees a return code of `ENOSPC` from a `semget`(2) call.
Commitment Level	Unstable

`semsys:seminfo_semmns`

Description	Maximum number of System V semaphores on the system.
Data Type	Signed integer
Default	60
Range	1 to MAXINT
Dynamic?	No
Validation	The amount of space that could possibly be consumed by the semaphores and their supporting data structures is compared to 25% of the kernel memory available at the time the module is first loaded. If the memory threshold is exceeded, the module refuses to load and the semaphore facility is not available.
When to Change	When the default number of semaphores is not enough. Generally changed at the recommendation of software vendors. No error messages are displayed when an attempt is made to create more semaphores than are currently configured. The application sees a return code of `ENOSPC` from a `semget`(2) call.
Commitment Level	Unstable