The optional GLOBALTCPIPDATA statement identifies a global TCPIP.DATA file, in which you can specify global settings. If you specify a global TCPIP.DATA file, you can control which resolver statements are used for name resolution and you do not need to merge resolver statements from multiple files. TCPIP.DATA statements in this file are the first that are searched, regardless of which socket API library you are using.
If you use a global TCPIP.DATA file, you can specify the following resolver statements, or you can use the default values. These statements are required by the resolver to process queries.
If you specify any of these statements in the global TCPIP.DATA file, those settings become the global settings for this MVS™ image and for all users of resolver services, across the entire system. If you do not specify one of these statements in the global TCPIP.DATA file, the resolver uses the default values. The search continues beyond the global TCPIP.DATA file, but any of these resolver statements that are specified in files that are located lower in the search order are ignored.
If you do not identify a global TCPIP.DATA file, then the resolver uses the regular search order until it finds a local TCPIP.DATA file.
If you do not specify one of these statements in this local TCPIP.DATA file, the resolver uses the default values. The setting that the resolver uses applies only to this application, not to all users of resolver services. In any case, the search order depends on whether the native MVS or z/OS® UNIX application environment is in use. The search order for the local hosts table (HOSTS.xxxxINFO, ETC.IPNODES, /etc/hosts, or /etc/ipnodes) remains the same.
You can specify other statements in the global TCPIP.DATA file (for information about configuration statements in TCPIP.DATA, see z/OS Communications Server: IP Configuration Reference). There are some statements, like TRACE RESOLVER, for which you likely do not want a global setting. If you do not specify one or more of these other statements in the global file, the resolver uses the regular search order until it finds a local TCPIP.DATA file. If you do not specify these other statements in the local TCPIP.DATA file, the resolver uses the default values.You can implement these global settings gradually, in case there are private TCPIP.DATA files that are in use on your system about which you are unaware.
You can identify a global TCPIP.DATA file in a CINET (common INET) environment. You specify in the global TCPIP.DATA file all the resolver statements for which you want to set a global value, and the resolver conducts its searches in the same way as in a non-CINET environment. However, if you do use a global TCPIP.DATA file in a CINET environment, all the resolver statements must be usable by all stacks. For example, the IP addresses that are specified by the NameServer statement must be accessible from all stacks. If the IP addresses are not accessible, then you should not use a global TCPIP.DATA file; use multiple TCPIP.DATA data sets instead. If you use multiple TCPIP.DATA data sets, you should not code the AUTOQUIESCE operand on the UNRESPONSIVETHRESHOLD statement in the resolver setup file.
You can use the DEFAULTTCPIPDATA setup statement to specify a TCPIP.DATA file as the last TCPIP.DATA file that is searched, instead of TCPIP.TCPIP.DATA. You can specify any file as the default file.