Technical data

4.5 ODS-5 and ODS-2 File Structures
OpenVMS implements On-Disk Structure Level 5 (ODS-5). This structure provides
the basis for creating and storing files with extended file names. The format was
introduced for compatibility with other file systems, such as Windows. You can
choose whether or not to convert a volume to ODS-5 on your OpenVMS Alpha
systems.
The ODS-5 volume structure provides the following features:
• Long file names
• More legal characters in file names
• Preservation of case in file names
These features are described in detail in the OpenVMS product documentation.
ODS-5 provides enhanced file-sharing capabilities for TCP/IP Services as well
as for Advanced Server for OpenVMS (or PATHWORKS for OpenVMS), DCOM,
and Java™ applications. Once ODS-5 volumes are enabled, some of the new
capabilities can impact certain applications or layered products as well as some
areas of system management.
The following sections summarize how the enabling of ODS-5 volumes can impact
system management, users, and applications.
4.5.1 Considerations for System Management
RMS access to deep directories and extended file names is available only on ODS-5
volumes mounted on OpenVMS Alpha Version 7.2 systems and higher. Compaq
recommends that ODS-5 volumes be enabled only on homogeneous OpenVMS
Alpha clusters. If ODS-5 is enabled in a mixed-version or mixed-architecture
OpenVMS Cluster, the system manager must follow special procedures and must
be aware of the following specific restriction: users must access ODS-5 files and
deep directories from OpenVMS Alpha systems only because these capabilities are
not supported on earlier versions of the operating system.
4.5.2 Considerations for Users
Users on OpenVMS Alpha systems can take advantage of all Extended File
Specifications capabilities on ODS-5 volumes that are mounted on those systems.
A user on a mixed-version or mixed-architecture OpenVMS Cluster is subject to
some limitations in ODS-5 functionality.
For detailed information about mixed-version or mixed-architecture support, refer
to the OpenVMS product documentation.
4.5.3 Considerations for Applications
You can select ODS-5 functionality on a volume-by-volume basis. If ODS-5 volumes
are not enabled on your system, all existing applications will continue to function
as before. If ODS-5 volumes are enabled, be aware of the following changes:
• OpenVMS file handling and command-line parsing are modified to enable
them to work with extended file names on ODS-5 volumes and maintain
compatibility with existing applications. The majority of existing, unprivileged
applications will work with most extended file names, but some applications
might need modifications to work with all extended file names.
4–4 OpenVMS Operating System TCP/IP Features