OpenVMS Guide to Extended File Specifications
OpenVMS Guide to Extended File Specifications
This document provides an overview of Extended File Specifications and
describes the impact of Extended File Specifications on system
managers, application developers, and users of the traditional OpenVMS
This manual supercedes the OpenVMS Guide to Extended File Specifications, Version 7.2.
OpenVMS Alpha Version 7.3 OpenVMS VAX Version 7.3
Compaq Computer Corporation Houston, Texas
© 2001 Compaq Computer Corporation
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statements accompanying such products. Nothing herein should be
construed as constituting an additional warranty.
The Compaq OpenVMS documentation set is available on CD-ROM.
This document is intended for system managers, application developers,
and users who implement Extended File Specifications on one or more
systems in an OpenVMS environment.
This manual consists of the following chapters and appendixes:
- Chapter 1 provides an overview of Extended File Specifications
and its features.
- Chapter 2 describes the changes visible to OpenVMS system
managers, provides instructions on how to enable and control user
access to ODS-5 volumes, and describes the impact on functions such as
backing up and restoring media.
- Chapter 3 describes the changes visible to OpenVMS users when
using ODS-5 volumes.
- Chapter 4 describes how to evaluate the support for Extended
File Specifications of OpenVMS applications.
- Appendix A contains guidelines for setting users' expectations
about using the features of Extended File Specifications.
- Appendix B contains detailed technical information about the
changes to the OpenVMS programming interface to support Extended File
Specifications. Much of this material appears in other documents in the
- Appendix C describes the DEC Multinational character set and the
ISO Latin-1 character set.
For related information about Extended File Specifications, see the
- Guide to OpenVMS File Applications
- OpenVMS DCL Dictionary: A--M
- OpenVMS DCL Dictionary: N--Z
- OpenVMS RTL Library (LIB$) Manual
- OpenVMS Record Management Services Reference Manual
- OpenVMS System Manager's Manual, Volume 1: Essentials
- OpenVMS System Manager's Manual, Volume 2: Tuning, Monitoring, and Complex Systems
- OpenVMS System Management Utilities Reference Manual: A--L
- OpenVMS System Management Utilities Reference Manual: M--Z
- OpenVMS System Services Reference Manual: A--GETUAI
- OpenVMS System Services Reference Manual: GETUTC--Z
- OpenVMS Utility Routines Manual
- Compaq Advanced Server for OpenVMS Server Administrator's
For additional information about OpenVMS products and
services, access the Compaq website at the following location:
Compaq welcomes your comments on this manual. Please send comments to
either of the following addresses:
Compaq Computer Corporation
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Overview of Extended File Specifications for OpenVMS
OpenVMS Version 7.2 on Alpha implements Extended File Specifications,
which consists of two major components:
- A new, optional, volume structure, ODS-5, which provides support
for file names that are longer and have a greater range of legal
characters than in previous versions of OpenVMS
- Support for deep directories
Taken together, these components provide much greater flexibility for
OpenVMS Alpha systems (using Advanced Server for OpenVMS 7.2, formerly known as
PATHWORKS for OpenVMS), to store, manage, serve, and access files that
have names similar to those in a Windows 95/98 or Windows NT
This chapter provides a brief overview of the benefits, features, and
support for Extended File Specifications, as well as changes in OpenVMS
behavior that occur under Extended File Specifications.
1.1 Benefits of Extended File Specifications
The deep directories and extended file names supported by Extended File
Specifications provide the following benefits:
- Users of Advanced Server for OpenVMS 7.2
(formerly known as PATHWORKS for OpenVMS) have the ability to store
longer file names, preserve the case of file names, and use deeper
directory structures. These new capabilities make the use of an OpenVMS
file server more transparent to Windows 95/98 and Windows NT users.
- OpenVMS system managers can see files on OpenVMS systems with the
names as specified by Windows 95/98 and Windows NT users.
- Applications developers who are porting applications from other
environments that have support for deep directories can use a parallel
structure on OpenVMS.
- Longer file naming capabilities and Unicode support enables
OpenVMS Version 7.2 to act as a
DCOM server for Windows NT clients, and ODS-5 provides capabilites that
make the OpenVMS and Windows NT environment more homogeneous for DCOM
JAVA applications on OpenVMS will comply with
JAVA object naming standards.
- General OpenVMS users can make use of long file names, new
character support, and the ability to have lowercase and mixed-case
These benefits result from the features described in Section 1.2.
1.2 Features of Extended File Specifications
Extended File Specifications consists of two main features, the ODS-5
volume structure, and support for deep directories. These features are
described in the sections that follow.
1.2.1 ODS-5 Volume Structure
OpenVMS Version 7.2 implements On-Disk Structure Level 5 (ODS-5). This
structure provides the basis for creating and storing files with
extended file names. You can choose whether or not to convert a volume
to ODS-5 on your OpenVMS Alpha systems.
The ODS-5 volume structure allows the following features:
- Long file names
- More characters legal within file names
- Preservation of case within file names
These features are described in the sections that follow.
22.214.171.124 Long File Names
On an ODS-5 volume, the name of a file (excluding the version number)
can be up to 236 8-bit or 118 16-bit characters long. Complete file
specifications longer than 255 bytes are abbreviated by RMS when
presented to unmodified applications.
For more information on extended file names, see Section 3.1.2.
126.96.36.199 More Characters Legal Within File Names
A broader set of characters is available for naming files on OpenVMS.
ODS-5 offers support for file names that use the 8-bit ISO Latin-1
character and 16-bit
Unicode (UCS-2) character sets.
ISO LATIN-1 and Unicode (UCS-2) Character Sets
The ISO Latin-1 Multinational character set is a superset of the
traditional ASCII character
set used by versions of OpenVMS previous to Version 7.2. In extended
file specifications, all characters from the 8-bit ISO Latin-1
Multinational character set are valid in file specifications,
except the following:
C0 control codes (0x00 to 0x1F inclusive)
Double quotation marks (")
Left and right angle brackets (< >)
Question mark (?)
Vertical bar (|)
To unambiguously enter or display certain special characters in an
ODS-5 compliant file specification, such as a space, you must precede
the character with a
For more information on how these character sets are used in file
names, see Section 3.1.2.
188.8.131.52 Preservation of Case
In prior versions of OpenVMS, DCL, RMS, and the file system converted
all file specifications to uppercase. ODS-5 preserves the case of file
specifications. For example:
$ CREATE x.Y
As you can see, the mixed-case of the file name is preserved.
For more information on case sensitivity, see Section 184.108.40.206.
1.2.2 Deep Directory Structures
Both ODS-2 and ODS-5 volume structures support deep nesting of
directories, subject to the following
- There can be up to 255 levels of directories.
- The name of each directory can be up to 236 8-bit or 118 16-bit
For example, a user can create the following deeply nested directory:
$ CREATE/DIRECTORY [.a.b.c.d.e.f.g.h.i.j.k.l.m]
A user can create the following directory with a long name on an ODS-5
Complete file specifications longer than 255 bytes are abbreviated by
RMS when presented to unmodified applications.
220.127.116.11 Directory Naming Syntax
On an ODS-5 volume, directory names conform to most of the same
conventions as file names when using the ISO Latin-1
character set. Periods and special characters can be present in the
directory name, but in some cases, they must be preceded by a
circumflex (^) in order to be recognized as literal characters.
Section 3.2 contains more information about deep directories.
Section 3.6.1 contains information about displaying long directory names.
1.3 Considerations Before Enabling ODS-5 Volumes
ODS-5 is being introduced primarily to provide enhanced file sharing
capabilities for users of Advanced Server for OpenVMS 7.2
(formerly known as PATHWORKS for OpenVMS), as well as
DCOM and JAVA applications.
Once ODS-5 volumes are enabled, some of the new capabilities can
potentially impact certain applications or layered products, as well as
some areas of system management. The new syntax for file names that is
allowed on ODS-5 volumes cannot be fully utilized on ODS-2 volumes.
Because pre-Version 7.2 Alpha systems cannot access ODS-5 volumes, and
Open VMS Version 7.2 VAX systems have limited ODS-5 functionality, you
must be careful where and how you enable ODS-5 volumes in mixed-version
and mixed-architecture OpenVMS Clusters.
The following sections comprise a summary of how enabling ODS-5 volumes
can impact system management, users, and applications.
1.3.1 Considerations for System Management
RMS access to deep directories and extended file names is available
only on ODS-5 volumes mounted on OpenVMS Alpha V7.2 systems. Compaq
recommends that ODS-5 volumes be enabled only on a homogeneous OpenVMS
Alpha V7.2 Cluster.
If ODS-5 is enabled in a mixed-version or mixed-architecture OpenVMS
Cluster, the system manager must follow special procedures and be aware
of specific restrictions on mixed-version and mixed-architecture
OpenVMS Clusters with ODS-5 volumes enabled:
- Users must access ODS-5 files and deep directories from OpenVMS
Alpha V7.2 systems only, because these capabilities are not supported
on earlier versions.
- Users who have created deep directories can view those directories
only from OpenVMS Alpha V7.2 systems.
- Pre-Version 7.2 systems cannot mount an ODS-5 volume nor read ODS-2
or ODS-5 file names on that volume.
Section 1.3.2 describes in greater detail the limitations of ODS-5
support for users in a mixed-version or mixed-architecture OpenVMS
Most unprivileged applications will work with most extended file names,
but some may need modifications to work with all extended file names.
Privileged applications that use physical or logical I/O to disk and
applications that have a specific need to access ODS-5 file names or
volumes may require modifications and should be analyzed. See the
website www.openvms.compaq.com for a list of fully supported OpenVMS
applications. Section 1.3.3 describes in greater detail the impact of
ODS-5 on OpenVMS applications.
Chapter 2 contains more information for determining the levels of
support for Extended File Specifications, and guidelines for managing a
system with ODS-5 volumes enabled.
1.3.2 Considerations for Users
A user on an OpenVMS Alpha Version 7.2 system can take advantage of all
Extended File Specifications capabilities on ODS-5 volumes mounted on
an OpenVMS Alpha Version 7.2 system.
A user on a mixed-version or mixed-architecture OpenVMS Cluster is
subject to some limitations in ODS-5 functionality. Section 18.104.22.168 lists
those restrictions that exist on a mixed-version OpenVMS Cluster.
Section 22.214.171.124 lists those restrictions that exist on a
mixed-architecture OpenVMS Cluster.
126.96.36.199 Mixed-Version Support
Systems running prior versions of OpenVMS cannot mount ODS-5 volumes,
correctly handle extended file names, or even see extended file names.
The following sections describe support on OpenVMS Version 7.2 and on
prior versions of OpenVMS in a mixed-version cluster.
Users on OpenVMS Alpha Version 7.2 Systems
A user on an OpenVMS Alpha Version 7.2 system can continue to access
pre-Version 7.2 files and directories; for example, a user can do all
of the following:
- Create and access deep directory structures on ODS-2 volumes.
- Read a BACKUP saveset created on an earlier version of OpenVMS.
DECnet to copy a file with an ODS-5 name to a file with an ODS-2 name
on a system running an earlier version of OpenVMS.
Users on Pre-Version 7.2 Systems
On mixed-version clusters, some restrictions exist. Users on a version
of OpenVMS prior to Version 7.2:
- Cannot access any files on an ODS-5 volume. This is true regardless
of whether the volume is connected physically on a CI or SCSI bus, or
by an MSCP or QIO server.
- Cannot successfully create or restore an ODS-5 image saveset.
However, these users can successfully restore ODS-2-compliant file
names from an ODS-5 saveset.
188.8.131.52 Mixed-Architecture Support
Current ODS-2 volume and file management functions remain the same on
both VAX and Alpha Version 7.2 systems; however, extended file naming
and parsing are not available on VAX systems.
The following sections describe support on OpenVMS VAX and Alpha
systems in a mixed-architecture cluster.
Limited Extended File Specifications Capabilities on VAX Systems
In mixed-architecture OpenVMS Version 7.2 clusters, OpenVMS Version 7.2
VAX systems are limited to the following Extended File Specifications
- Ability to mount an ODS-5 volume
- Ability to write and manage ODS-2-compliant files on an ODS-5
- See pseudonames (
) when accessing an ODS-5 file specification
From a VAX system, users cannot successfully create or restore an ODS-5
image saveset. However, these users can successfully restore
ODS-2-compliant file names from an ODS-5 saveset.
1.3.3 Considerations for Applications
ODS-5 functionality can be selected on a volume-by-volume basis. If
ODS-5 volumes have not been enabled on your system, all existing
applications will continue to function as before. If ODS-5 volumes have
been enabled, you need to be aware of the following changes:
- OpenVMS file handling and command line parsing have been modified
to enable them to work with extended file names on ODS-5 volumes while
still being compatible with existing applications. The majority of
existing, unprivileged applications will work with most extended file
names, but some may need modifications to work with all extended file
- Privileged applications that use physical or logical I/O to disk
may require modifications and should be analyzed. Applications that
have a specific need to access ODS-5 file names or volumes should be
analyzed to determine if they require modification.
On ODS-5 volumes, existing applications and layered products that are
coded to documented interfaces, as well as most DCL command procedures,
should continue to work without modification.
However, applications that are coded to undocumented interfaces, or
include any of the following, may need to be modified in order to
function as expected on an ODS-5 volume:
- Internal knowledge of the file system, including knowledge of:
The data layout on disk
The contents of file headers
The contents of directory files
- File parsing tailored to a particular on-disk structure.
- Assumptions about the syntax of file specifications, such as the
placement of delimiters and legal characters.
- Assumptions about the case of file specifications. Mixed and
lowercase file specifications will not be converted to uppercase, which
can affect string matching operations.
- Assumptions that file specifications are identical between RMS and
the file system.
All unmodified XQP applications running on an OpenVMS VAX or Alpha
system that access an ODS-5 volume will see pseudonames returned in
place of Unicode or ISO Latin-1 names that are not ODS-2 compliant.
This can cause applications to act in an unpredictable manner.
Applications that specify or retrieve filenames with the XQP interface
using ODS-5 disks must be modified in order to access files with
See Chapter 4 for further discussion of the support status of