To take advantage of the near real-time availability information that ADNR can provide regarding sysplex resources, clients must query the ADNR-managed name servers relatively frequently rather than use cached information from a previous name server query. The length of time that name server information is cached is typically controlled by the Time To Live (TTL) value received from the name server. A TTL is associated with each resource record in a name server, and the TTL information is part of the information that the resolver receives when the name server successfully responds to a query. ADNR provides a mechanism to define the TTL for name server resources it manages.
ADNR permits the TTL to be defined to a specific value per zone, or it can be set to a value determined by the GWM, which is the default. When the TTL value is the default value determined by the GWM, it takes on the update_interval value in the Advisor's configuration file.
Because ADNR can be configured to use a GWM-defined interval to set the TTL value, the GWM can dynamically change this interval. The z/OS® Load Balancing Advisor does not support dynamically changing this interval, but a future Advisor implementation or other future GWM implementations might. If this occurs, ADNR has the capability to find out about the new GWM interval only when the connection to the GWM is re-established.