System Maximums - HP A4500A - VMEbus Single Board Computer 744 Motherboard Programmer's Manual

Note that if an ACSE/Presentation call (such as ap_open()) fails because
of temporary memory shortage, the application may want to retry the
same call later.

System Maximums

OTS supports up to 4096 virtual circuit (VC) connections at the transport
and network layer (X.25 CONS). If applications such as X.400 or FTAM
are also in use, note that each session access connection also uses a
transport connection. If XTI API applications are also in use, note that
each XTI connection also uses a transport connection. The number of
X.25 VCs supported may be further limited by hardware configuration
limits and the number and type of X.25 interface cards.
The system has no priority for connection requests versus data transfers
on existing connections. It is recommended that an application
successfully bring up all required connections before transferring data.
Connection management should not occur during data transfer. The
application pacing should avoid possible timing problems.
Process Maximums
It is possible to have a single process use up to the maximum number of
connections. Under these circumstances, observe the following
restrictions:
• A low rate of incoming data, including connect indications.
• Incoming events do not occur at the same time on all of the
connections. Too many concurrent events can overflow buffers. The
AP_AGAIN error may occur more often.
• The application should receive incoming events as soon as possible to
regularly poll the connection for events.
• Check burst rate.
• Check pacing of execution watching for timing errors.
• Check if the number of connections gradually increases or decreases.
Because communication endpoints are file descriptors, the maximum
number of communication endpoints (and connections) per process is
limited by the maximum number of open files allowed per process by HP-
UX. The number of connections allowed per process is further limited by
any other files opened by the process.
Chapter 4
Programming Guide
5. Managing Multiple Connections
61