OSF DCE Application Development Guide--Core Components

RPC and Other DCE Components
/.:/Bldg/Print_server_host_7
/.:/Bldg/Print_server_host_9
4. The search selects the /.:/Bldg/Print_server_host_9 entry. This entry contains
both a server address for the requested Version 2.1 of the interface and the
requested object UUID of the Laser_printer queue:
/.:/Bldg/Print_server_host_9 contents:
print_server-if-uuid, 2.1
binding-information
laser_printer_queue-object-uuid
The search returns binding information from this entry to the client.
14.3.2.3 Expiration Age of a Local Copy of Directory Service Data
To prevent accessing a namespace unnecessarily, previously requested directory
service data is sometimes stored on the system where the request originated. A local
copy of directory service data is not automatically updated at each request. Automatic
updating of the local copy occurs only when it exceeds its expiration age. The
expiration age is the amount of time that a local copy of directory service data from an
NSI attribute can remain unchanged before a request from an RPC application for the
attribute requires updating of the local copy. When an RPC application begins
running, the RPC runtime randomly specifies a value between 8 and 12 hours as the
default expiration age for that instance of the application. Most applications use only
this default expiration age, which is global to the application.
An expiration age is used by an NSI next operation, which reads data from directory
service attributes. For a given search or inquire operation, you can override the
default expiration age by calling the routine rpc_ns_mgmt_handle_set_exp_age( )
after the operation’s begin routine. Note that specifying a low default age will result
in increased network updates among the name servers in your cell. This will adversely
affect the performance of all network traffic. Therefore, use the default whenever
possible. If you must override the default age, specify a number that is high enough to
avoid frequent updates of local data.
An NSI next operation usually starts by looking for a local copy of the attribute data
being requested by an application. In the absence of a local copy, the NSI next
operation creates one with fresh attribute data from the namespace. If a local copy
already exists, the operation compares its actual age to the expiration age used by the
application. If the actual age exceeds the expiration age, the operation automatically
tries to update the local copy with fresh attribute data. If updating is impossible, the
old local data remains in place and the NSI next operation fails, returning the
rpc_s_name_service_unavailable status code.
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