Host address is not resolved correctly

When you see problems where TCP/IP Resolver cannot resolve the host address properly, it is most likely due to a missing or incomplete resolver configuration file. A clear indication for this problem is the following message in lock.log:
clientip(0.0.0.0) <> callerip(<host IP address>)
To verify this, execute the fekfivpt TCP/IP IVP, as described in "Installation verification" in the Host Configuration Guide (SC27-8437). The resolver configuration section of the output will look like the following sample:
Resolver Trace Initialization Complete -> 2008/07/02 13:11:54.745964

res_init Resolver values:
 Global Tcp/Ip Dataset  = None
 Default Tcp/Ip Dataset = None
 Local Tcp/Ip Dataset   = /etc/resolv.conf
 Translation Table      = Default
 UserId/JobName         = USERID
 Caller API             = LE C Sockets
 Caller Mode            = EBCDIC

Ensure that the definitions in the file (or data set) referenced by “Local Tcp/Ip Dataset” are correct.

This field will be blank if you do not use a default name for the IP resolver file (using the z/OS® UNIX search order). If so, add the following statement to rse.env, where <resolver file> or <resolver data> represents the name of your IP resolver file:

RESOLVER_CONFIG=<resolver file>

or

RESOLVER_CONFIG=’<resolver data set>’