NM and CM callable.
Creates or acquires an extra data segment for use by the process.
Data segment management (DS) capability is required.
Operation Notes |
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The number of extra data segments that can be requested, and the
maximum size allowed these segments, is limited by parameters
specified when the system is configured. When an extra data segment
is created, the GETDSEG intrinsic returns a logical
index number to the process. This index number is assigned by
the operating system and allows the process to reference the extra data
segment in later intrinsic calls.
Assign the extra data segment to an identity that either
allows other processes in the job or session to share the extra
data segment, or that declares it private to the calling
process. If the extra data segment is shareable, other processes
can obtain its index (through GETDSEG) and use this index to
reference the extra data segment. Thus, the index is a local name
that identifies the extra data segment throughout any process
that obtained the index with the GETDSEG call. The index does not
need to be the same value in all processes sharing the extra data segment.
However, the identity is a job-wide or session-wide name
that permits any process to determine the index of the extra data segment.
If GETDSEG is called in user mode,
the extra data segment is initially filled with zeros.
When GETDSEG is called in user mode, all subsequent calls to
intrinsics that use index must be in user mode.
When GETDSEG is called in privileged mode, all subsequent calls to
intrinsics that use index must be in privileged mode.
When a data segment is created through GETDSEG, sufficient
virtual space is allocated by the system to accommodate the original
length of the data segment. This virtual space is allocated in increments
of 512 half words. For example, creation of an extra data segment with a
length of 600 half words results in the allocation of 1024 half words
of virtual space.
