OSF DCE Application Development Guide--Core Components

OSF DCE Application Development Guide—Core Components
4. In stage D, the called procedure has completed call 1, making the call thread
available. The server has removed call 2 from the queue and is passing it to the
call thread for execution. Thus, the queue is partially empty as call 12 arrives, so
the server accepts the call and adds it to the queue.
16.6.4 Selecting a Manager
Unless an RPC interface is implemented for more than one specific type of object,
selecting a manager for an incoming call is a simple process. When registering an
interface with a single manager, the server specifies the nil type UUID for the manager
type.
1
In the absence of any other manager, all calls, regardless of whether they request
an object, go to the nil type manager.
The situation is more complex when a server registers multiple managers for an
interface. The server runtime must select from among the managers for each incoming
call to the interface. The DCE RPC dispatching mechanism requires a server to set a
nonnil type UUID for a set of objects and for any interface that will access the objects in
order to register a manager with the same type UUID.
To dispatch an incoming call to a manager, a server does the following:
1. If the call contains the nil object UUID, the server looks for a manager registered
with the nil type UUID (the nil type manager).
a. If the nil type manager exists for the requested interface, the server
dispatches the call to that manager.
b. Otherwise, the server rejects the call.
2. If the call contains a nonnil object UUID, the server looks to see whether it has set
a type for the object (by assigning a nonnil type UUID).
If the object lacks a type, the server looks for the nil type manager.
a. If the nil type manager exists for the requested interface, the server
dispatches the call to that manager.
b. Otherwise, the server rejects the call.
3. If the object has a type, the call requires a remote procedure of a manager whose
type matches the object’s type. In its absence, the RPC runtime rejects the call.
Figure 16-8 illustrates the decisions a server makes to select a manager to which to
dispatch an incoming call.
________________
1 The API uses NULL to specify a synonym to the address of the nil UUID, which contains only zeros.
16 − 44 Tandem Computers Incorporated 124245