HP OpenVMS Version 8.3 for Alpha and Integrity Servers
HP OpenVMS Version 8.3 for Alpha and Integrity Servers SPD 82.35.11
Other failures include:
• Operating system errors (system-detected inconsis-
tencies or architectural errors in system context)
• User errors
• I/O errors
The system logs all processor errors, all operating
system errors detected through internal consistency
checks, all double-bit memory errors (and a summary
of corrected single-bit memory errors), and most I/O er-
rors.
If the system is shut down because of an unrecoverable
hardware or software error, a dump of physical mem-
ory is written. The dump includes the contents of the
processor registers. The OpenVMS System Dump An-
alyzer (SDA) utility is provided for analyzing memory
dumps.
Input/Output
The QIO system service and other related I/O services
provide a direct interface to the operating system’s I/O
routines. These services are available from within most
OpenVMS programming languages and can be used to
perform low-level I/O operations efficiently with a mini-
mal amount of system overhead for time-critical appli-
cations.
Device drivers execute I/O instructions to transfer data
to and from a device and to communicate directly with
an I/O device. Each type of I/O device requires its own
driver. HP supplies drivers for all devices supported
by the OpenVMS operating system and provides QIO
system service routines to access the special features
available in many of these devices.
OpenVMS supports a variety of disk and tape periph-
eral devices, as well as terminals, networks, and mail-
boxes (virtual devices for interprocess communication),
and more general I/O devices.
I/O Performance Features
Fast I/O provides a suite of additional system services
that applications can use to improve I/O throughput. The
fast I/O services minimize the CPU resources required
to perform I/O.
Fast Path provides a streamlined mainline code path
through the I/O subsystem to improve both uniproces-
sor and multiprocessor I/O performance. On multipro-
cessor systems, Fast Path allows all CPU processing for
specific I/O adapters to be handled by a specific CPU.
This can significantly lower the demands on the primary
CPU and increase the I/O throughput on multiproces-
sor systems with multiple I/O ports. No user application
changes are needed to take advantage of Fast Path.
Fast Path can be utilized by the $QIO system service
or the Fast I/O services.
Extended File Cache (XFC)
The Extended File Cache (XFC) is a virtual block data
cache provided with OpenVMS Alpha and OpenVMS for
Integrity servers. Similar to the Virtual I/O Cache, the
XFC is a clusterwide, file system data cache. Both file
system data caches are compatible and coexist in the
OpenVMS Cluster.
The XFC improves I/O performance with the following
features that are not available with the virtual I/O cache:
• Read-ahead caching
• Automatic resizing of the cache
• Larger maximum cache size
• No limit on the number of closed files that can be
cached
• Control over the maximum size of I/O that can be
cached
• Control over whether cache memory is static or dy-
namic
Virtual I/O Cache (Alpha only)
OpenVMS Alpha provides a standalone or clusterwide,
file-oriented disk cache. Applications benefit from the
advantages of the virtual I/O cache without any special
coding. The virtual I/O file-caching algorithm is chosen
based on the type of clusterwide access currently in
progress. Virtual I/O caching reduces current and po-
tential I/O bottlenecks within OpenVMS systems. It re-
duces the number of I/Os to the disk subsystem, thereby
reducing systemwide bottlenecks.
Record Management Services (RMS)
RMS is a set of I/O services that helps application pro-
grams to process and manage files and records. Al-
though it is intended to provide a comprehensive soft-
ware interface to mass storage devices, RMS also sup-
ports device-independent access to unit-record devices.
RMS supports sequential, relative, and indexed file or-
ganizations in fixed-length or variable-length record for-
mats. RMS also supports byte stream formats for se-
quential file organization.
RMS record access modes provide access to records
in four ways:
• Sequentially
• Directly by key value
• Directly by relative record number
• Directly by record file address
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