HP OpenVMS Systems Documentation

HP OpenVMS Programming Concepts Manual

Alpha OpenVMS Version 7.2 and greater and OpenVMS I64 implement Extended File Specifications, which consists of two major components:

• An 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 formerly known as PATHWORKS for OpenVMS), to store, manage, serve, and access files that have names similar to those in a Windows environment. Advanced Server support for OpenVMS I64 is planned for a subsequent release.

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.

For more information about extended file specifications, see the Guide to OpenVMS File Applications, and the HP OpenVMS System Manager's Manual.

29.1 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 V7.2 and later (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 users.
• OpenVMS system managers can see files on OpenVMS systems with the names as specified by Windows 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 to act as a DCOM server for Windows clients, and ODS-5 provides capabilites that make the OpenVMS and Windows environment more homogeneous for DCOM developers.
• 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 file names.

These benefits result from the features described in Section 29.2.

29.2 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.

29.2.1 ODS-5 Volume Structure

OpenVMS 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 and OpenVMS I64 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.

29.2.1.1 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.

29.2.1.2 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 as of OpenVMS Version 8.2, except the following:

Asterisk (*)
Question mark (?)

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 circumflex (^).

29.2.1.3 Preservation of Case

On ODS-5 disks on Alpha and I64 systems, the Extended File Specifications support preserving case (as in uppercase and lowercase letters). If a file is created with lowercase letters from program control, the name, as stored on disk, is lowercase.

From the DCL command interface, file names that are entered at the command prompt with lowercase letters will be translated by default to uppercase before they are passed to RMS. Case may be preserved from the DCL command interface by using the DCL command SET PROCESS/PARSE_STYLE=EXTENDED (also see the SYS$SET_PROCESS_PROPERTIESW system service).

File look-ups, however, are case-blind. For example, the filename "File.Txt" (as stored on an ODS-5 disk) could be accessed with a reference to "FILE.TXT" or "file.txt".

An option may be set for file look-ups at either the process or file level to request RMS to either ignore or notice the case sensitivity of file names on ODS-5 disks.

At the process level, the user may request RMS to ignore case by using SET PROCESS/CASE_LOOKUP=BLIND. If a file on an ODS-5 disk already exists whose name matches that of a file being created except for its case, the new file will be created with the same case as the existing file (rather than with the case as entered). This is the default behavior. In contrast, the user may request RMS to notice case by using SET PROCESS/CASE_LOOKUP=SENSITIVE (also see the SYS$SET_PROCESS_PROPERTIESW system service). If the SENSITIVE option is in effect and the user creates more than one file on an ODS-5 disk with the same name differing only in case, each file is treated as a new file.

At the file level, the NAML$V_CASE_LOOKUP flag can be used to instruct RMS to ignore or notice case for a file on an ODS-5 disk (see the NAM$L_INPUT_ FLAGS field in the NAML structure in the OpenVMS Record Management Utilities Reference Manual. NAML$C_CASE_BLIND is set to tell RMS to ignore case or NAML$C_CASE_LOOKUP_SENSITIVE to notice case when creating, deleting or searching for a file on an ODS-5 disk. If the NAML structure is not used or this flag is zero, the current process setting for CASE_LOOKUP is used.

The SET PROCESS/PARSE_STYLE qualifier is independent of the /CASE_ LOOKUP qualifier. If the creation, deletion, or search of files on an ODS-5 disk is being done using the DCL command interface and case is relevant, /PARSE_STYLE=EXTENDED must be used to inform the DCL interface to preserve the case specified in the DCL command. The /CASE_LOOKUP qualifier instructs RMS whether to ignore or notice the case (either preserved or not).

29.2.2 Deep Directory Structures

Both ODS-2 and ODS-5 volume structures support deep nesting of directories, subject to the following limits:

• 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 characters long.

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 volume:

$ CREATE/DIRECTORY
[.AVeryLongDirectoryNameWhichHasNothingToDoWithAnythingInParticular]

Complete file specifications longer than 255 bytes are abbreviated by RMS when presented to unmodified applications.

29.2.2.1 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.

29.3 Considerations Before Enabling ODS-5 Volumes

ODS-5 provides 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.

29.3.1 Considerations for System Management

RMS access to deep directories and extended file names is available only on ODS-5 volumes mounted on OpenVMS I64 and OpenVMS Alpha V7.2 and greater systems. HP recommends that ODS-5 volumes be enabled only on a homogeneous OpenVMS I64 or OpenVMS Alpha V7.2 and greater 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 I64 and OpenVMS Alpha V7.2 and greater systems only, because these capabilities are not supported on earlier versions.
• Users who have created deep directories can view those directories only from OpenVMS I64 and OpenVMS Alpha V7.2 and greater 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 29.3.2 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 http://h71000.www7.hp.com for a list of fully supported OpenVMS applications. Section 29.3.4 describes in greater detail the impact of ODS-5 on OpenVMS applications.

29.3.2 Considerations for Users

Users of OpenVMS I64 and OpenVMS Alpha Version 7.2 and higher systems can take advantage of all Extended File Specifications capabilities on ODS-5 volumes mounted on an OpenVMS I64 and OpenVMS Alpha Version 7.2 and greater system.

Users of mixed-version or mixed-architecture OpenVMS Clusters are subject to some limitations in ODS-5 functionality. Section 29.3.2.1 lists those restrictions that exist on a mixed-version OpenVMS Cluster. Section 29.3.2.2 lists those restrictions that exist on a mixed-architecture OpenVMS Cluster.

29.3.2.1 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 greater and on prior versions of OpenVMS in a mixed-version cluster.

OpenVMS I64 and OpenVMS Alpha Version 7.2 and Higher Systems

OpenVMS I64 and OpenVMS Alpha Version 7.2 and higher system can continue to access pre-Version 7.2 files and directories; for example, users 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.
• Use 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 of 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.

Current ODS-2 volume and file management functions remain the same on VAX, Alpha Version 7.2 and greater systems, and I64 systems; however, extended file naming and parsing are not available on VAX systems.

The following sections describe support on OpenVMS VAX, Alpha, and I64 systems in a mixed-architecture cluster.

Limited Extended File Specifications Capabilities on VAX Systems

In mixed-architecture OpenVMS Version 7.2 and greater clusters, OpenVMS Version 7.2 and greater VAX systems are limited to the following Extended File Specifications functionality:

• Ability to mount an ODS-5 volume
• Ability to write and manage ODS-2-compliant files on an ODS-5 volume
• See pseudonames ( \pISO_LATIN\.??? or \pUNICODE\.??? ) when accessing an ODS-5 file specification

BACKUP Limitations

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.

29.3.3 NFS Support for Extended File Specifications

The NFS server and the NFS client support OpenVMS extended file specifications (EFS) on ODS-5 disk volumes.

You can use NFS server to export files on OpenVMS ODS-5 volumes. The traditional ODS-2 volumes continue to be supported. The NFS client can emulate an ODS-5 volume.

Note that the NFS server and NFS client support the ISO Latin-1 character set only.

If an ODS-5 volume is mapped and exported, the NFS server automatically supports EFS features and ignores the NAME_CONVERSION option of the EXPORT command, if it is specified in the export record.

On ODS-2 volumes (with or without the NAME_CONVERSION option), files with all uppercase names are displayed on non-OpenVMS clients with all lowercase letters. On ODS-5 volumes, the file names are displayed by clients in the same case as they are displayed locally on the server host.

If an ODS-2 volume contains file names that were created using the NAME_CONVERSION option of the NFS EXPORT command and include lowercase or special characters that are invalid for ODS-2 file names, those file names displayed locally on the server host contain character sequences (escape codes), as described in HP TCP/IP Services for OpenVMS Management. If the DCL SET VOLUME /STRUCTURE_LEVEL=5 command is performed on this volume, the names are displayed by clients with the character sequences exactly as they are displayed locally on the server host.

29.3.4 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.

This section describes considerations for applications and how to evaluate an application's support for Extended File Specifications.

29.4.1 Evaluating Your Current Support Status

Any applications that are coded to undocumented interfaces may not provide support for either deep directories or extended file names. Section 29.4.3 lists additional application attributes that may prevent an application from supporting extended file names. Section 29.4.4 lists additional application attributes that may prevent an application from supporting ODS-5 volumes.

You can choose either to modify these applications to support Extended File Specifications or not to use them under Extended File Specifications. For information on how to modify an application to provide default support for Extended File Specifications, see Section 29.5.1. For information on how to upgrade an application to full support, see Section 29.5.2.

29.4.2 Default Support

Most unmodified OpenVMS applications fall into the default support category. Specifically, these applications use the traditional API rather than the new API when making RMS calls. Applications that use high-level language calls to perform file operations will also fit into this category unless the language run-time libraries have been modified to full support. In most cases, you will not need to modify these applications for them to function successfully under Extended File Specifications.

29.4.3 No Support for Extended File Names

An application that does any of the following may not support extended file names:

1. Uses the QIO interface to specify file names. Developers should examine all layered products and applications and evaluate any file name interaction between the RMS and the XQP interfaces. The format for extended file names varies for each interface. As a result, an application can no longer assume that it can use the same file name for both RMS and the XQP. In addition, the XQP does not allow an unmodified application to use extended file names. Valid file names could differ between interfaces.
2. Makes assumptions about the syntax of file specifications, such as the placement of delimiters and legal characters.
3. Makes assumptions about the case of file specifications. RMS no longer converts mixed and lowercase file specifications to uppercase in all cases. This could affect string matching operations.
4. Depends on the traditional directory depth (fewer than 8 levels).

An application that uses internal knowledge of the file system, including knowledge of the contents of a directory and how file header data is structured on a disk cannot work correctly on an ODS-5 volume.

29.5 Upgrading an Application to Support Extended File Specifications

The following sections describe the changes necessary to upgrade the level of support for extended file specifications. Note that you must first ensure that the application meets the default support level before you can upgrade it to the full support level.

To upgrade an application to provide default support for Extended File Specifications, you must ensure that it minimally supports both the ODS-5 volume structure and extended file naming as recommended in naming as recommended in Sections 29.5.1.1 and 29.5.1.2, respectively. Default support is defined in Section 29.4.2.

29.5.1.1 Providing Support for ODS-5

Applications that do not support the new ODS-5 volume structure do not operate successfully on these volumes even if they encounter only traditional file specifications.

If an application does not work properly on an ODS-5 volume, examine the application for the following:

• Does the application use physical or logical I/O to bypass the file system when accessing the volume, or does it access metadata files such as BITMAP.SYS directly? These applications are usually system programs, such as disk defragmenters, or programs that try to avoid overhead by accessing the disk directly. These applications rely on specific knowledge of the file or directory structure on the disk, which has changed with introduction of the ODS-5 structure.
  Recommendation: Applications should use documented interfaces and structures whenever possible.
• Does the application access and interpret the contents of directory files directly? If so, the application may fail when it encounters a directory that contains extended file names.
  Recommendation: Modify the application to use the search functions provided with the RMS or QIO interface, or with LIBRTL routines such as LIB$FIND_FILE.