gethostbyname()

When a host name is specified with an SNMP request, the SNMP Query Engine looks up the IP address of that host. It uses the standard gethostbyname() function to perform that function. The IP address is then saved in an in-memory cache for future references. For more information about gethostbyname(), see z/VM: TCP/IP Programmer's Reference.

The cache cannot be refreshed, and if for some reason the mapping between host names and IP addresses changes, the SNMP Query Engine (the SQESERV module) has to be restarted to rebuild its cache. This is also true for a host name that was found to be nonexistent at the time of the first SNMP request, but which has been added to the name server database.

This gives a performance boost to subsequent requests for the same host.