Open System Services Management and Operations Guide (G06.29+, H06.07+)

Introducing Open System Services
Open System Services Management and Operations Guide—527191-005
1-15
Interprocess Communication Facilities
OSS shell commands allow you to manage OSS message queues, OSS shared
memory, and OSS semaphores; these commands are discussed further in Section 2,
Operating the OSS Environment.
OSS Message Queues
Message queues are linked lists of messages used by programmers to pass data from
one process to another. In the OSS environment, the OSS message-queue server
process named $ZMSGQ manages the message queues.
Message queues cannot be used unless the OSS message-queue server is running.
The OSS message-queue server can be started by the OSS SCF Monitor START
SERVER Command, as described in Starting the OSS Message-Queue Server.
Pipes and FIFOs
Pipes are unnamed connections between two OSS application processes that are
used to send or receive data. FIFOs are pipes with names. Pipes and FIFOs are
special files in UNIX terminology, rather than regular files.
An OSS pipe server process named $ZPPnn runs in each processor (nn indicates the
processor number). The OSS pipe server supports the transfer of data between OSS
processes that use pipes or FIFOs between processors.
Like the OSS file manager, the OSS pipe server starts automatically when the
processor starts; if the OSS pipe server terminates abnormally, it takes down the
processor. Its processor can be shut down without first stopping the process, but you
should stop all applications with open OSS pipes or FIFOs first.
Because you do not need to manage the OSS pipe server, pipes and FIFOs are not
discussed further in this guide and the OSS pipe server is not shown in Figure 1-4 on
page 1-10.
OSS Sockets
In addition to the OSS message-queue server and the OSS name servers, your
system needs servers to provide an OSS application program with access to OSS
sockets. OSS sockets facilities are separate from the sockets facilities provided within
the Guardian environment.
There are two kinds of OSS sockets, named after the address families used to send
and receive data through them. OSS sockets include:
•
AF_UNIX sockets, sometimes called local or UNIX domain sockets
•
AF_INET or AF_INET6 sockets, sometimes called Internet domain sockets
When AF_UNIX sockets are used or AF_INET sockets are used with HP NonStop
TCP/IP:
•
OSS sockets route data between application processes using a process called a
transport agent and a process called a transport provider