GDSX Manual

Operations and Support
Extended General Device Support (GDSX) Manual–134303
3-12
User Data Segment
Regarding the data space, GDSX uses a user data segment with a size of 64 pages.
TSCODE uses two extended segments—one for various control and data structures and
one for trace data. The segment allocated by default for the control and data structures
is segment ID 1024. Segment ID 1025 is always allocated for the trace data. Segment
IDs from 1024 up are reserved for TSCODE.
Although it is generally not advisable, USCODE can use its own extended segment
through calls to ALLOCATESEGMENT and USESEGMENT. The segment IDs
available to USCODE range from 0 to 1023.
User Data Segment
The user data segment of the GDSX process is specified at bind time to have a size of
64K words. The size of various areas within the segment is determined by the
configuration parameters. (See “GDSX Configuration Parameters” on page 2-42 and
page 3-12.)
Extended Segment
GDSX allocates an extended segment (with default segment ID 1024) and a size
determined by the configuration parameters. If the space is not available, GDSX will
not run, and an internal error message is created—abend error 30.
Extended Segments for Trace Files
When the trace facility is turned on in the primary GDSX process, TSCODE allocates an
extended segment with segment ID 1025, a default size of 64 pages, and the default file
name TRACEP under the default subvolume. The SCF TRACE command may be used
to specify a different file name, and the USER^OPEN^TRACE^FILE procedure may be
used to specify a different file size. (For further information regarding the trace facility,
see “Tracing GDSX” on page 2-76.)
When the trace facility is turned on in the backup process, TSCODE allocates an
extended segment with segment ID 1025, a default size of 64 pages, and the file name
TRACEB under the default subvolume.
If the specified trace file does not exist, the GDSX process creates and uses the file. If
the default subvolume already has a file with the name specified and the file has not
been opened by another process, the GDSX process opens the file. If the specified trace
file is in use by any other process, the GDSX process will not initiate the trace.
GDSX Configuration Parameters
GDSX uses configuration parameters to control memory allocation and numerous
aspects of the run-time environment. Some configuration parameters are called static,
because once their values are determined at process creation time, they cannot be
changed. The other configuration parameters are called dynamic because their values
can be changed after the process has been initialized.
See “GDSX Configuration Parameters” on page 2-42 for detailed information about the
static and dynamic configuration parameters for GDSX.