Specifications

OpenVMS VAX Operating System, Version 5.5-2 SPD 25.01.37
VMS RMS promotes safe and efficient file sharing by
providing multiple file access modes, automatic record
locking where applicable, and optional buffer sharing by
multiple processes.
VMS RMS utilities aid file creation and record mainte-
nance. These utilities convert files from one organiza-
tion and format to another, restructure indexed files for
storage and access efficiency, and reclaim data struc-
tures within indexed files. The utilities also generate
appropriate reports.
For systems that have DECnet installed, VMS RMS pro-
vides a subset of file and record management services
to remote network nodes. Network remote file opera-
tions are generally transparent to user programs.
DCL commands such as EDIT, CREATE, COPY, TYPE,
and PRINT allow manipulation of RMS files and records
within RMS files at the DCL command level.
RMS Journaling for OpenVMS
RMS Journaling for OpenVMS is a VMS System Inte-
grated Product (SIP) that enables a system manager,
user, or application to maintain the data integrity of RMS
files in the face of a number of failure scenarios. It pro-
tects RMS file data from becoming lost, corrupted, or in-
consistent. RMS Journaling for OpenVMS is separately
licensed.
RMS Journaling provides the ability to maintain three
types of journaling that maintain modification information
for journaled RMS files.
• Before Image Journaling. Provides the ability to
"undo" modifications that have been made to a file.
This type of journaling provides the ability to return
a file to a previous known state. This is useful in
the event that a file is updated with erroneous or bad
data. No application modifications are necessary in
order to use Before Image journaling.
• After Image Journaling. Provides the ability to "redo"
modifications that have been made to a file. This type
of journaling allows you to recover files that are in-
advertently deleted, lost or corrupted. RMS Journal-
ing recovers the file by applying the journaled modi-
fications to a backup copy, thereby restoring its final
state. No application modifications are necessary in
order to use After Image journaling.
• Recovery Unit Journaling. Provides the ability to
maintain transaction integrity. A transaction may be
defined as a series of many file updates, on one or
more files. In the event of any failure during the trans-
action, Recovery Unit journaling will roll-back the par-
tially completed transaction to its starting point. This
allows complex transactions to be completed as an
atomic event - partially completed transactions can
be avoided. Recovery Unit journaling requires appli-
cation modification.
Refer to SPD 27.58.xx for more information.
Disk and Tape Volumes
Disk volumes can be organized into volume sets. Vol-
ume sets can contain a mix of disk device types and
can be extended by adding volumes. Within a volume
set, files of any organization type can span multiple vol-
umes. Files can be allocated to the set as a whole (the
default) or to specific volumes within the set. Optionally,
portions of indexed files can be allocated to specific ar-
eas of a single disk volume or to specific volumes in a
volume set.
Disk quotas can be placed to control the amount of
space individual users can allocate. Quota assignment
is made by User Identification Code and can be con-
trolled for each volume set in the system (or for each
individual volume if the volume is not part of a set).
Disk structure information can be cached in memory to
reduce the I/O overhead required for file management
services. Although not required to do so, users can
preallocate space and control automatic allocation. For
example, a file can be extended by a given number of
blocks, contiguously or noncontiguously, for optimal file
system performance in specific cases.
The system applies software validity checks and check-
sums to critical disk structure information. If a volume
is improperly dismounted because of user error or sys-
tem failure, the system automatically rebuilds the vol-
ume’s structure information the next time the volume
is mounted. The system detects bad blocks dynami-
cally and prevents their reuse once the files to which the
blocks were allocated are deleted. On Digital Storage
Architecture (DSA) disks, the disk controller dynamically
detects and replaces bad blocks automatically.
The system provides eight levels of named directories
and subdirectories whose contents are alphabetically or-
dered. Device and file specifications follow Digital con-
ventions. Logical names can be used to abbreviate the
specifications and to make application programs device
and file-name independent. A logical name can be as-
signed to an entire specification, to a portion of a spec-
ification, or to another logical name.
VMS supports multivolume magnetic tape files with
transparent volume switching. Access positioning is
done either by filename or by relative file position.
Volume Shadowing for OpenVMS
Digital provides the Volume Shadowing for OpenVMS
product for performing disk shadowing operations, using
a RAID 1 implementation.
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