GDSX Manual

Design and Development
Extended General Device Support (GDSX) Manual–134303
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Transaction Management Facility
primary process. The task’s last checkpoint block in the former backup’s extended
memory of size TASKCPSIZE is searched for an address match. When one is found,
space in the specified buffer pool is allocated and the data image is copied. Finally, the
word pointer in the task’s stack is updated to point to the new location of the data. For
more information, see the description of the ^RECLAIMBUFFER procedure in
Section 8.
A Second Takeover
When designing a GDSX application, consider what happens if a takeover occurs, and
then a second takeover occurs before a task checkpoints.
Transaction Management Facility
The Transaction Management Facility (TMF) subsystem is the main functional
component of the NonStop Transaction Manager/MP (TM/MP) product on Tandem
NonStop systems. TMF is used to protect transactions originating from user tasks of a
GDSX application. GDSX supports four pseudo TMF procedures:
•
^ABORTTRANSACTION
•
^BEGINTRANSACTION
•
^ENDTRANSACTION
•
^RESUMETRANSACTION
Except for ^BEGINTRANSACTION, these pseudo procedures have the same syntax
and function as their TMF counterparts. You must set the TMF configuration parameter
to 2 to have these procedures work properly from a user task.
TMF Configuration Parameter
The TMF configuration parameter can be set for three processing modes:
Caution. Following a takeover, if a task does not recover all its buffer images before it does a
type 2 checkpoint, those buffers not reclaimed are lost.
Caution. Following a takeover, if a task recovers its buffer images with ^RECLAIMBUFFER but
does not do a type 2 checkpoint before a second takeover occurs, after the second takeover
the task’s buffer images are lost.
Mode Description
0 TSCODE does not permit any TMF processing from a user task, and it will not
pass a TMF transaction from an external process to another process, such as
Pathway. This is the default setting.
1 TSCODE does not permit any TMF processing from a user task; however, it will
pass a TMF transaction from an external process to another process.
2 TSCODE permits TMF processing from a user task, but it will not pass a TMF
transaction from an external process to another process.