Diagnosing and resolving Resolver problems

Table 1. Diagnosing and resolving Resolver problems
Symptoms	Problem/Cause	Action
No IP addresses were resolved from the TargetServer configuration statements. EZD1815E (during initialization) is issued or EZD1845I (MODIFY REFRESH or MODIFY REFRESHIPLIST command) is issued. See the appropriate EZD1815E, EZD1845I messages in z/OS Communications Server: IP Messages Volume 2 (EZB, EZD).	Possible causes for this error are: The Resolver is not initialized. There may be a problem in the DNS or the Resolver setup. The name specified on the TargetServer statement (TargetName or TargetMx parameter) may be incorrect.	If the resolver is not initialized, start the resolver. See the appropriate EZD1815E, EZD1845I messages in z/OS Communications Server: IP Messages Volume 2 (EZB, EZD). If the name on the TargetServer is in error, update the name and issue the MODIFY REFRESH command to reprocess the configuration file. If the name on the TargetServer statement is correct, investigate your DNS and/or resolver setup.
Updated IP addresses were resolved from the TargetServer configuration statements with warnings. EZD1847I is issued. See the appropriate EZD1847I message in z/OS Communications Server: IP Messages Volume 2 (EZB, EZD).	Possible causes for this warning are: A TargetName or TargetMx name could not resolve to any IP address A TargetName or TargetMx name resolved to more than 4 IP addresses	Verify that the name specified on the TargetName or TargetMx parameter is correct. If the name is in error, update the name and issue the MODIFY REFRESH command to reprocess the configuration file. If the name is correct, investigate your DNS and/or resolver setup. If more than four addresses are resolved for a name specified on a TargetServer statement, only the first four are allowed and the rest ignored. Note: A warning is informational and no action is required.
No changed IP addresses were resolved from the TargetServer configuration statements as a result of the MODIFY REFRESH command or MODIFY REFRESHIPLIST command. EZD1843I or EZD1844I is issued. See the appropriate messages in z/OS Communications Server: IP Messages Volume 2 (EZB, EZD).	If changed IP addresses were expected, then it might indicate a problem. The name specified on the TargetServer statement may not be updated with the new name. The name specified on the TargetServer statement was changed, but the updates in the DNS or the Resolver setup may not be refreshed.	Verify that the name specified on the TargetName or TargetMx parameter is correct. If the name is in error, update the name and issue the MODIFY REFRESH command to reprocess the configuration file. Refresh the resolver so that the response is not coming from the cache, then issue the MODIFY REFRESHIPLIST command to refresh the TargetName or TargetMx
MODIFY REFRESH or REFRESHIPLIST unsuccessful due to a MODIFY COMMAND in progress. EZD1806I is issued. See the appropriate EZD1806I message in z/OS Communications Server: IP Messages Volume 2 (EZB, EZD).	DNS setup may be in error causing the MODIFY COMMAND to take a long time.	Check if DNS is active at the IP address you specified for the NameServer or NSINTERADDR in the TCPIP.DATA data set. Check the port that DNS is listening on. The port is specified on the NSPORTADDR in the TCPIP.DATA data set.

The Resolver trace shows requests and responses sent to and received from name servers. It also shows if local hosts tables are used for name resolution. This trace helps you diagnose problems with host name resolution. See TRACE RESOLVER for more information about how to activate Start of change Trace Resolver End of change and collect output.