HP-UX System V IPC Message Queues

A System V message is a sequence of bytes that can be passed between cooperating processes via a message queue.

HP-UX Sys V IPC message queues are enhanced with dynamic tuning capabilities.

Summary of Change

What’s New for Customers Migrating from HP-UX 11i v1 September 2005?

HP-UX Sys V IPC message queues kernel tunable configuration parameters are enhanced with dynamic tuning capabilities.

Tunables msgmax, msgssz, msgmap, msgseg are obsolete in HP-UX 11i v3.
New dynamic tunable msgmbs is added, which indicates the maximum (in megabytes) kernel memory to be used for messages waiting to be received. This new tunable replaces the function of the obsolete msgssz and msgseg tunables. Lowering the tunable value has no effect on any active messages, even if the new tunable value is less than the total number of message bytes currently enqueued. However, no new messages may be queued until the total number of bytes falls below the setting of msgmbs.
Tunables msgmni, msgtql are made dynamic. These tunables can be increased or decreased dynamically with out rebooting the machine. Lowering msgtql has no effect on any queued messages, even if the new tunable value is less than the number of queued messages. However, no new messages may be queued until the number of messages falls below the setting of msgtql. Lowering msgmni has no effect on any active message queues, even if the new tunable value is less than the number of queues created in the system. However, no new queues may be created until the number of active queues falls below the setting of msgmni.
The tunable msgmnb is unchanged.

Dynamic tuning adjustments to msgmbs, msgmni, msgtql may be done using SAM or the kernel configuration command kctune.




	TIP: To find information about obsoleted kernel tunables listed in this document, perform a search on the word “tunable”.

What’s New for Customers Migrating from HP-UX 11i v2 June 2006?

See “What’s New for Customers Migrating from HP-UX 11i v1 September 2005?”

Impact

You will be able to change System V Message Queue parameters and have those changes effective immediately without the need to reboot the system.

Compatibility

On system update, site-specific settings of msgseg, msgssz will be replaced with a site-specific setting of msgmbs. It is set to the value of (msgssz*msgseg) rounded to megabytes.

Performance

There is no impact on performance.

Documentation

For further information, see the manpages msgmap(5), msgseg(5), msgssz(5), msgmax(5), mesg(5), msgmni(5), msgtql(5), and msgmbs(5).

Obsolescence

Not applicable.