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The signal options specify an additional set of attributes for the signal monitor.
The primary use of these options is to specify an additional set of actions to be
taken by the system when a signal-catching function is called.
A signal is generated by sending a request to a signal monitor.
The process to receive the signal is identified by a process ID. The process ID is
used to indicate whether the signal should be sent to an individual process or to a
group of processes (known as a process group). The process ID is used to locate
an entry in the system-managed process table. A process table entry contains the
following information relating to the process:
Parent process ID
Process group ID
Status information
The parent process is the logical creator of the process. A process group repre-
sents a collection of processes that are bound together for some common purpose.
The process sending a signal must have the appropriate authority to the receiving
process.
The OS/400 support for signals does differ from the usual behavior of signals on
UNIX systems.
For additional information about signal concepts, OS/400 management support, and
how signals differ on OS/400 from UNIX systems, see the “Signal Concepts” topic
in the book
System API Reference
.
Simple Network Management Protocol (SNMP) APIs
The Simple Network Management Protocol (SNMP) APIs comprise the SNMP sub-
agent APIs and the SNMP manager APIs.
SNMP Subagent APIs:
The SNMP subagent APIs can be used to dynamically
extend the management information base (MIB) that the system SNMP agent is
aware of. The MIB is extended without any change to the SNMP agent itself while
the AS/400 is running. Dynamically added MIB subtrees (as supported and defined
by a program known as a subagent) provide this capability. You may now extend
the remote and automated system management capabilities of the AS/400 within
the SNMP framework. So, for example, you could define an SNMP MIB group for
your RPG and SQL application.
The Distributed Protocol Interface (DPI) is an extension to SNMP agents. DPI
permits users to dynamically add, delete, or replace management variables in the
local MIB without requiring recompilation of the SNMP agent.
SNMP Manager APIs:
SNMP managing applications typically use APIs to estab-
lish communication with local or remote SNMP agents, and then call other APIs to
retrieve or modify MIB objects managed by those agents. The OS/400 SNMP
manager APIs accomplish both of these tasks within the same API. Three
manager APIs are provided to perform the SNMP GET, GETNEXT, and SET oper-
ations. In general, all three APIs are blocked, that is, once the application calls
these APIs, the API constructs a proper SNMP message, delivers it to the proper
SNMP agent, waits, decodes the response from the agent, and delivers the infor-
mation to the application. No processing occurs in the application until the API
Chapter 8. Use of OS/400 APIs 8-25