Specifications

OpenVMS Operating System for Alpha and VAX (Versions 7.1, 7.1–1H1, 7.1–1H2, and 7.1–2) SPD 41.87.06
The presence of vector support code in a system has
little effect on processes running in a scalar-only sys-
tem, or scalar processes running in a vector-present
system. If many processes must compete simultane-
ously for vector processor resources, the system man-
ager can maintain good performance by adjusting sys-
tem resources and process quotas.
The OpenVMS VAX operating system makes the ser-
vices of the vector processor available to system users
by means of a software abstract known as a capabil-
ity. A system manager can restrict the use of the vector
processor to users holding a particular identifier by as-
sociating an ACL entry with the VECTOR object.
The VAX Vector Instruction Emulation Facility (VVIEF) is
a standard feature of the OpenVMS VAX operating sys-
tem. It allows vectorized applications to be written and
debugged in a VAX system in which vector processors
are not available. VVIEF emulates the VAX vector pro-
cessing environment, including the nonprivileged VAX
vector instructions and the OpenVMS VAX vector sys-
tem services. Use of VVIEF is restricted to code in user
mode.
DECdtm Services
The DECdtm services embedded in the OpenVMS oper-
ating system support fully distributed databases using a
two-phase commit protocol. The DECdtm services pro-
vide the technology and features for distributed process-
ing, ensuring both transaction and database integrity
across multiple Compaq resource managers. Updates
to distributed databases occur as a single all-or-nothing
unit of work, regardless of where the data physically re-
sides. This ensures the consistency of distributed data.
DECdtm services allow applications to define global
transactions that can include calls to any number of
Compaq data management products. Regardless of
the mix of data management products used, the global
transaction either commits or stops. OpenVMS is
unique in providing transaction processing functionality
with base operating system services.
DECdtm features include:
• Embedded OpenVMS system services that support
the DECtp architecture, providing the features and
technology for distributed transaction processing.
• The ability for multiple disjoint resources to be up-
dated atomically. These resources can be ei-
ther physically disjointed (for example, on different
CPUs) or logically disjointed (for example, in differ-
ent databases on the same CPU).
• Robust application development. Applications can
be written to ensure that data is never in an incon-
sistent state, even in the event of system failures.
• Can be called using any Compaq TP monitor or
database product. This is useful for applications us-
ing several Compaq database products.
Interprocess Communication
OpenVMS provides the following facilities for applica-
tions that consist of multiple cooperating processes:
• Mailboxes as virtual devices that allow processes to
communicate with queued messages.
• Shared memory sections on a single processor or an
SMP system that permit multiple processes to access
shared address space concurrently.
• Common event flags that provide simple synchro-
nization.
• A lock manager that provides a more comprehen-
sive enqueue/dequeue facility with multilevel locks,
values, and asynchronous system traps (ASTs).
Symmetric Multiprocessing (SMP)
OpenVMS provides symmetric multiprocessing (SMP)
support for Alpha and VAX multiprocessor systems.
SMP is a form of tightly coupled multiprocessing in
which all processors perform operations simultaneously.
The processors can perform operations in all OpenVMS
access modes, such as user, supervisor, executive, and
kernel.
OpenVMS SMP configurations consist of multiple CPUs
executing code from a single shared memory address
space. Users and processes share a single copy of
OpenVMS Alpha or OpenVMS VAX address space.
SMP also provides simultaneous shared access to com-
mon data in global sections to all processors. OpenVMS
SMP selects the CPU where a process will run based
on its priority.
SMP support is an integral part of OpenVMS and is
provided to the user transparently. Because an SMP
system is a single system entity, it is configured into
a network and OpenVMS Cluster configurations as a
single node.
Networking Facilities
OpenVMS provides device drivers for all Compaq local
area network (LAN) adapters listed in the LAN Options
section of Appendix A of this SPD. Application program-
mers can use the QIO system service to communicate
with other systems connected via the LAN using either
Ethernet or Institute of Electrical and Electronics En-
gineer (IEEE) 802.3 packet format. Simultaneous use
of Compaq Ethernet and the IEEE 802.3 protocols are
supported on any Compaq LAN adapter.
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