Open System Services Management and Operations Guide (G06.30+, H06.08+, J06.03+)

OSS Shared Memory and Semaphores
Semaphores allow one process to signal another about events such as the status of data in memory
shared by the processes. OSS shared memory and semaphores are implemented using NonStop
operating system features and do not require any installation or configuration actions before use.
The Guardian environment has separate facilities for shared memory and semaphores that are not
discussed in this guide.
OSS shell commands allow you to manage OSS message queues, OSS shared memory, and OSS
semaphores; these commands are discussed further in “Operating the OSS Environment” (page 46).
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 “START SERVER Command” (page 313).
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 3 (page 34).
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_UNIX sockets include
AF_UNIX Release 1 sockets and AF_UNIX Release 2 sockets. Beginning with the J06.05 and
later J-series RVUs and H06.16 and later H-series RVUs, AF_UNIX Release 2 sockets and
software completely replaces AF_UNIX Release 1 sockets and software. AF_UNIX Release 1
sockets and AF_UNIX Release 2 sockets do not coexist on the same system.
• 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.
• Multiple transport-provider processes can be used to create separately addressed IP subnetworks
within a node.
• AF_INET sockets utilize AF_INET socket data buffers.
Components to Be Managed 39