OSI/AS Programming Manual

Connection Endpoint Identifier (CEPI)
APS Procedures Programming Concepts
056783 Tandem Computers Incorporated 2–21
A dynamic subdevice exists until you call APS_DISCARD_ to discard the connection
context. With dynamic subdevices, the linkage between a TAPS process and the lower
layers must be reestablished whenever you call APS_ASSOC_ATTACH_ or
APS_ASSOC_CONNECTREQ_; that takes time.
A static subdevice, by contrast, is not deleted when you call APS_DISCARD_. With
static subdevices, your application can reuse existing linkages between a TAPS process
and the lower layers for successive connections, thereby reducing system overhead.
When you are finished using a subdevice, you explicitly delete it by calling
APS_SUBDEVICE_DISCARD_.
Each application name will use either dynamic or static subdevices exclusively,
depending upon how you have configured the particular application name. For
information about application names and how to configure them for the use of
dynamic and static subdevices, refer to the Tandem OSI/AS Configuration and
Management Manual.
Reusing Static Subdevices A static subdevice can be reused only:
With the same PSAP address, AP title, and AE qualifier
With the same type of request (attach or connect)
On the same service layer (ACSE, presentation, or session)
When using either APS_ASSOC_ATTACH_ or APS_ASSOC_CONNECTREQ_ with a
static subdevice, the correct sequence of events is as follows:
1. Call the particular procedure, specifying a local application name that was
configured for using static subdevices (this creates a CEPI and a subdevice).
You can explicitly name the subdevice by including subdevice-name in the call;
if you do not, then OSI/AS will automatically name the subdevice for you.
2. Issue an APS_STATUS_ call to obtain the fully qualified subdevice name.
3. When you are finished using the connection, call APS_DISCARD_ to discard the
connection context and close the subdevice.
4. Issue another APS_ASSOC_CONNECTREQ_ or APS_ASSOC_ATTACH_ call,
specifying the subdevice name obtained in step 2. This procedure call, which
creates another CEPI and reopens the static subdevice, will be completed more
quickly than the one performed in step 1.
Note When reusing a static subdevice in an APS_ASSOC_ATTACH_ call, you must either omit the local
application name from the procedure call or supply a null value. When reusing a static subdevice in an
APS_ASSOC_CONNECTREQ_ call, you must either omit both the local and remote application names
from the procedure call or supply null values.
5. When you are finished using the connection, call APS_DISCARD_ to discard the
connection context and close the subdevice.
6. Repeat steps 4 and 5 as often as necessary.