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The common design scenarios for the Reso... > Using the Resolver address space in ... - Pg. 25

2.3.1 Using the Resolver address space in a single stack environment To set up an environment with global definitions, it is important to understand how these definitions affect the entire environment, and also which statements must always be defined once we create this global environment. To implement the global settings, we use a setup data set that has parameters to address the Resolver config file to be used as global or as a default file; so in our first scenario, we use the following steps to include the global definitions in our system: 1. Describe the environment that is going to be created. In this step, we define which statements we want to be defined as global parameters, and which ones we want to define as default, if any applications do not have it defined. 2. Define the names and location of the global and default Resolver configuration files. 3. Define how the Resolver procedure will be started. Describe the environment In this step, the global TCPIP.DATA data set will become the first TCPIP.DATA data set read regardless of the Socket API library being used. Any parameters found in this data set will be global settings for the z/OS LPAR. If a global TCPIP.DATA data set has been specified then all Resolver statements defined in it will only be obtained from this data set. The search continues beyond the file specified by GLOBALTCPIPDATA, but any of the Resolver statements specified in files lower in the search order will only be used if not specified explicitly in the global statements. In our scenario we want our system to have a common set of parameters that will not be changed by any application. We also want all queries to be searched on the local files first using the ETC.IPNODES data set. If it is not there, then query a name server. Figure 2-4 on page 26 shows the relationship between the Resolver procedure, which defines the setup data set, rssetup, where we will find the pointer to the Global Resolver configuration, called GLOBAL, and the global ipnodes, called IPNODES. We also defined the global ipnodes in the setup data set so all queries will address this data set locally, and defined the statement lookup in the global definitions to search the local files first and, if it is not there, then query the DNS. Chapter 2. The Resolver 25