Specifications

OpenVMS VAX Operating System, Version 5.5-2 SPD 25.01.37
VAXcluster CPUs communicate using any combination
of four interconnects; CI, DSSI, Ethernet, and FDDI.
VAXcluster systems that include a CI may optionally
be configured with HSC-series intelligent storage con-
trollers.
Applications running on one or more CPUs in a VAXclus-
ter system access shared resources in a coordinated
manner. VAXcluster Software components synchronize
access to shared resources, preventing multiple pro-
cesses on any CPU in the VAXcluster from interfering
with each other when updating data. This coordination
ensures data integrity during multiple concurrent update
transactions. Application programs can specify the level
of VAXcluster-wide file sharing that is required; access
is then coordinated by the VMS Extended QIO Proces-
sor (XQP) and Record Management Services (RMS).
The VMS queue manager controls VAXcluster-wide
batch and print queues, which can be accessed by any
VAXcluster CPU. Batch jobs submitted to VAXcluster-
wide queues are routed to any available CPU so that
the batch load is shared.
Two or more VAX computers connected to the same
Computer Interconnect (CI) or Digital Storage Systems
Interconnect (DSSI) must run VAXcluster software and
be part of the same VAXcluster system.
Refer to the VAXcluster Software Software Product De-
scription (SPD 29.78.xx) for more information.
Networking Facilities
VMS provides device drivers for all Digital Ethernet
adapters listed in the Ethernet Options section of this
SPD. Application programmers can use the QIO sys-
tem service to communicate with other systems con-
nected via the Ethernet using either Ethernet or IEEE
802.3 packet format. Simultaneous use of Digital Eth-
ernet and IEEE 802.3 protocols are supported on any
Digital Ethernet adapter.
VMS also provides device drivers for Digital asyn-
chronous adapters that are supported by DECnet–VAX.
Customers must order the VAX Wide Area Network
Device Drivers kit (refer to SPD 29.64.xx) to obtain
synchronous device drivers for Digital synchronous
adapters. Not all devices are supported, and certain
restrictions apply relative to line speed and line utiliza-
tion. Refer to the Hardware Charts and Appendix B of
this SPD, as well as the DECnet–VAX SPD (25.03.xx),
for more information.
DECnet–VAX offers task-to-task communications, file
management, downline system and task loading, net-
work command terminals, and network resource shar-
ing capabilities using the Digital Network Architecture
(DNA) protocols.
DECnet–VAX Software is a System Integrated Product
(SIP) that is separately licensed from the VMS Oper-
ating System. Refer to the DECnet–VAX SPD (SPD
25.03.xx) for further information on supported commu-
nications devices and software features.
Internet networking is available through the VMS/ULTRIX
Connection layered product. This product provides TCP
/IP networking (useful with DECwindows), Network File
System (NFS), File Transfer Protocol (FTP), Remote
Terminal Services (TELNET), and other features. Refer
to the VMS/ULTRIX Connection SPD (SPD 25.A4.xx).
Multi-Threading Capability
VMS includes a user-mode multi-threading capability re-
ferred to as DECthreads. DECthreads provides an im-
plementation of draft 4 of the proposed POSIX 1003.4a
standard and is Digital’s implementation of the Dis-
tributed Computing Environment (DCE) Threads as de-
fined by the Open Software Foundation. DECthreads
is a library of run-time routines that allows the user to
create multiple threads of execution within a single ad-
dress space. Multi-threading capability allows computa-
tion activity to be overlapped with I/O activity. Synchro-
nization elements, such as mutexes and condition vari-
ables, are provided to help ensure that shared resources
are accessed correctly. DECthreads also provides mul-
tiple scheduling policies for scheduling and prioritizing
threads.
Terminal Server Products
Digital’s terminal server products can be used for ter-
minal server access to VMS. When used in a VAXclus-
ter system environment, terminal servers automatically
distribute users at login time across the available VAX
systems.
VMS can also establish a connection to other devices
(such as printers) attached to such terminal servers.
Reliability
The system handles hardware errors as transparently
as possible while maintaining data integrity and provid-
ing sufficient information to diagnose the cause of the
error. The system limits the effects of an error by first
determining if the error is fatal. If the error is fatal then
the process that encountered the error is aborted. If the
error occurs in system context then the current VMS
session is shut down. If the error is not fatal then re-
covery actions pertinent to the error are executed and
current operation is continued.
In all cases, information relevant to the error is collected
and put in the error log file for later analysis. Hardware
errors include the following categories:
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