HP OpenVMS System Manager's Manual, Volume 1:...

Using Files and Directories

Understanding Extended File Specifications Features

Guidelines for Using Extended File Specifications on OpenVMS...

Considerations Before Enabling ODS-5 Volumes  

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.

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 and higher systems. HP recommends that ODS-5 volumes be enabled only on a homogeneous OpenVMS Cluster running Alpha V7.2 and later.

In versions of OpenVMS prior to Version 7.3-1, ODS-5 volumes could not be used as system disks, and it was recommended that ODS-5 disks be used in homogeneous Alpha clusters only. These restrictions have been removed. OpenVMS Version 7.3-1 and higher support the use of ODS-5 volumes as system disks and in heterogeneous Alpha clusters.

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.

Considerations for Users describes in greater detail the limitations of ODS-5 support for users in a mixed-version or mixed-architecture OpenVMS Cluster.

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.hp.com/go/openvms for a list of fully supported OpenVMS applications. Considerations for Applications describes in greater detail the impact of ODS-5 on OpenVMS applications.

Levels of Support for Extended File Specifications contains more information for determining the levels of support for Extended File Specifications.

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. Mixed-Version Support lists those restrictions that exist on a mixed-version OpenVMS Cluster. Mixed-Architecture Support lists those restrictions that exist on a mixed-architecture OpenVMS Cluster.

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 names.



• 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 extended names.

1	The HP file and print server that evolved from the PATHWORKS for OpenVMS (Advanced Server) to support the Windows NT integration features introduced with OpenVMS Version 7.2 on Alpha.

( Number takes you back )

Understanding Extended File Specifications Features

Guidelines for Using Extended File Specifications on OpenVMS...