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Chapter 2: The Resolver > Overview - Pg. 18

2.1 Overview A Resolver is a set of routines that act as a client on behalf of an application to read a local host file or to access one or more Domain Name System (DNS) for name-to-IP address or IP address-to-name resolution. Where the Resolver looks for name-address resolution and how it handles requests, is defined in a file called the Resolver configuration file. The Resolver can exist on any system that supports sockets programs, using name resolution. On a z/OS system, the Resolver configuration data is located either in an z/OS dataset (TCPIP.DATA) or in a file (resolv.conf) in the z/OS UNIX file system. Note: The z/OS V1R7.0 Communications Server: IP Configuration Guide, SC31-8775, contains useful information about the characteristics that are required for the z/OS data sets or file system files that contain resolver setup and configuration statements. The Guide also points out the security characteristics and file system permission settings that are needed. The Resolver configuration on z/OS can be somewhat complex, because of the flexibility provided to control how the Resolver behaves based on the socket environment and local preferences. The Resolver function in a z/OS environment is performed by a component called the Resolver address space , which was introduced to simplify the configuration tasks. 2.1.1 Basic concepts In most systems, for the application to reach a remote partner, it uses two commands to ask