TS/MP 2.5 Release Supplement

1 Application Cluster Services (ACS) Subsystem
The Application Cluster Services provide link-management functions for applications using Pathsend
requestors on the NonStop server platform.
ACS replaces the traditional TS/MP 2.0 LINKMON (TS/MP ROUT) process to provide the Pathsend
functionality on the system.
This section includes these topics:
• “Architecture Overview” (page 12)
• “ACS Domains” (page 15)
• “Security” (page 15)
• “Improved Application Availability” (page 16)
• “Pathway Domain Configuration Management” (page 17)
• “ACSCTL File Configuration” (page 18)
• “Configuration and Environment Limits” (page 20)
• “Link Management” (page 21)
• “System Management Interface” (page 22)
• “Pathsend API” (page 22)
• “Application Programming Compatibility and Pathway Domains” (page 24)
• “Load Balancing PATHMON Link Requests in a Pathway Domain” (page 25)
• “Process Management” (page 26)
• “PATHTCP4” (page 26)
• “Statistics Collection” (page 26)
• “Error Handling” (page 27)
Architecture Overview
The following processes are the basic components in the ACS subsystem:
• “Domain Coordinator Process ($ZACS)” (page 14)
• “Process Broker Process ($ZPnn)” (page 14)
• “Configuration Subscriber Process ($ZCSnn)” (page 14)
• “Redirector (ROUT) Process ($ZLnn)” (page 14)
The domain coordinator process manages a single instance of each process broker (PB),
configuration subscriber, and redirector (ROUT) process that is replicated in all CPUs in a NonStop
system. Only one instance of the domain coordinator process exists per NonStop system.
The PB, configuration subscriber, and redirector processes coordinate with other processes to
provide link-management functions, as shown in Figure 1 (page 13). The processes share memory
and are tightly bound. If any of these processes fail, the other processes may also fail.
As shown in Figure 1 (page 13), the domain coordinator process also shares memory with the PB,
configuration subscriber, and redirector process in the CPU in which it resides and is, therefore,
also tightly bound to the processes in that CPU.
Figure 1 (page 13) and Figure 2 (page 14) show only one PATHMON and PATHCOM process.
However, a system can contain multiple PATHMON and PATHCOM processes, in addition to,
multiple server classes and clients.
12 Application Cluster Services (ACS) Subsystem