Management information base (MIB)

The information maintained at each agent is defined by a set of variables known as the management information base, or MIB. In addition to the architected list of variables that must be supported by each SNMP agent, an SNMP agent can also support user-defined variables. These user-defined variables that are not part of the architected MIB are known as enterprise-specific MIB variables.

On z/OS® Communications Server, the majority of the MIB variables are maintained outside the SNMP agent address space by programs known as SNMP subagents. The subagent program for the TCP/IP-related MIB variables executes in the TCP/IP address space. The subagent program for OMPROUTE-related MIB variables run as part of OMPROUTE, not as a separate application. The subagent program for SLA-related MIB variables runs as a separate application. The subagent program for TN3270E Telnet server MIB variables executes as a separate subtask in the TN3270E Telnet server address space. For a list of all the MIB objects supported by the agent and subagents shipped as part of z/OS Communications Server, see z/OS Communications Server: IP System Administrator's Commands.

In addition, user-written subagent programs can also exist. All subagent programs, whether provided by z/OS Communications Server or user-written, communicate with the SNMP agent over an architected interface known as the Distributed Protocol Interface, or DPI.

When the SNMP agent receives and authenticates a request, it passes the request to the DPI subagent that has registered as the target of the request. You can see this exchange by enabling DPI tracing within the agent.