For implementations that cache name service data, the expiration age is the maximum amount of time, in seconds, that a cached copy of data from a name service attribute is considered valid by name service operations that read data from a name service. When there is no cached copy, the operation creates one with fresh data from the name service database. When there is a cached copy, the operation compares its age with the calling application's expiration age. If the copy's age exceeds the expiration age, the operation attempts to update the cached copy with fresh data from the name service. Fresh data is always retrieved from the name service.
Every application maintains a global expiration age value.
Applications may also set the expiration ages of individual name service handles. Whenever a name service operation is performed using a handle for which the application has not set an expiration age, the global expiration age value is used. In implementations that cache name service data, setting the expiration age to a small value may cause operations that retrieve data from the name service to update cached data frequently. Frequent updates may adversely affect the performance both of the calling application and any other applications that share the same cache. Permissions Required None.