ULTRIX Guide to the Location Broker

This document, the "Guide to the Location Broker" for ULTRIX Version 4.0+, is intended for system administrators. It describes the administration of the Location Broker, a key component of Digital Remote Procedure Call (DECrpc) that provides name service runtime support for distributed applications using remote procedure calls.

The Location Broker consists of three main components:

1. Local Location Broker (LLB): The llbd daemon, running on each host with RPC servers, maintains a database of local objects and interfaces and acts as a forwarding agent.
2. Global Location Broker (GLB): The nrglbd daemon, typically run on a single host per network (or glbd on Apollo systems for replication/reliability), maintains network-wide object and interface information.
3. Location Broker Client Agent: Library routines that allow applications to register servers and look up object/interface locations within the LLB and GLB databases using Universal Unique Identifiers (UUIDs).

The guide details the lb_admin administrative tool, which enables administrators to inspect, add, delete, and clean entries in Location Broker databases, particularly useful for error correction or manual registration.

It provides guidelines for configuring and starting both LLB (llbd) and GLB (nrglbd) daemons, emphasizing the correct startup order (LLB then GLB then RPC servers) and considerations for heterogeneous networks (e.g., Apollo systems). Finally, the manual covers maintenance procedures, including changing the GLB host, recovering from host crashes (e.g., by backing up GLB database or re-registering servers), and the importance of gracefully terminating RPC servers to avoid stale entries in the broker databases.