GDSX (Extended General Device Support) Manual

Design and Development
Extended General Device Support (GDSX) Manual—529931-001
2-21
Extended Segment for Control Structures
Extended Segment for Control Structures
For various control and data structures, GDSX allocates an extended segment with a
size determined by the configuration parameters. Unless you specify a different
segment by means of the SEGMENTID configuration parameter, segment ID 1024 is
allocated. (See Descriptions of Configuration Parameters on page 2-51.) If the space
is not available, GDSX will not run, and an internal error message is created (abend
error 30).
See Figure 2-2 for a summary of the contents of the extended segment. Areas
illustrated in this table have distinct boundaries and appear in the order shown, except
for those areas in the diagram from the table of checkpointed buffers down to and
including the statistics table (or the $RECEIVE queue if the statistics table is not
allocated), which are typically intermingled and checkerboarded over the space
allocated for all of them.
A user task is assigned space in the table of checkpointed buffers when it first calls
^CHECKPOINT(2). A user task is assigned space in the stack image area when it is
started; an equal amount of space will be allocated at the task’s first call to
^CHECKPOINT. The statistics table is allocated only if stats^flag is set (see the
description of CONTROLFLAGS on page 2-52); space in this table is assigned when a
LINE or a preconfigured SU is added. Unprinted log messages are stored in the LOG
message queue.
Figure 2-1. User Data Segment
TSCODE global primary area
size = 128 words
User globals (bound in)
maximum size of user global primary area = 128 words
User global secondary area also available
Buffer pool
Area extends from end of user globals to %73000 (to 29.5K words)
Working data stack
maximum size = 2000 words
Free space (unused)
size = 524 words
LOG message buffer
size = 256 words
Message pool
Area extends from end of LOG message buffer to %177777 (64K words)
Hash table used to search RCB pool
size = 524 words
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