Ext File Specs, Overview
*Conan The Librarian
Extended File Specifications includes support for the following: o The ODS-5 disk structure. ODS-5 is an extension to the existing ODS-2 disk structure, and adds the ability to use extended file names that can be more easily mapped between Windows and OpenVMS. ODS-5 expands the available character set and filename length to be consistent with Windows 95 and Windows NT, and sets the stage for future Unicode file name support through PATHWORKS. o Deeper directories. Enhancements to RMS provide deep directory support on both ODS-2 and ODS-5 volumes. 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 or Windows NT environment. This topic provides an overview of the benefits, features, and support for Extended File Specifications, as well as changes in OpenVMS behavior that occur when using Extended File Specifications.
|1 - Benefits|
The deep directories and extended file names supported by Extended File Specifications provide the following benefits: o OpenVMS system managers can manage files with extended names and deep directories in the same manner as Windows NT users. o Users of Advanced Server for OpenVMS 7.2 (formerly known as PATHWORKS for OpenVMS) have the ability to store longer file names and use deeper directory structures, which are more compatible with Windows 95 and Windows NT file names. o Applications developers who are porting applications from other environments that have support for deep directories can use a parallel structure on OpenVMS. o Longer file naming capabilities and Unicode support enables OpenVMS Alpha Version 7.2 and later 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 developers. o JAVA applications on OpenVMS will comply with JAVA object naming standards. o General OpenVMS users can make use of long file names, new character support, and the ability to have lowercase and mixed-case file names.
|2 - Features|
Extended File Specifications consists of two main features, the ODS-5 volume structure, and support for deep directories.
2.1 - ODS-5
OpenVMS Alpha Version 7.2 and later 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 enable ODS-5 volumes on your OpenVMS Alpha systems. The ODS-5 volume structure allows the following features: o Long file names o More characters legal within file names o Preservation of case within file names
2.2 - Deep Directories
Both ODS-2 and ODS-5 volume structures support deep nesting of directories, subject to the following limits: o There can be up to 255 levels of directories. o The name of each directory can be up to 236 8-bit or 117 16-bit characters long. Complete file specifications longer than 255 bytes are abbreviated by RMS when presented to unmodified applications. 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]
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.
|3 - Considerations|
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. System managers must understand the impact of an ODS-5 environment before enabling it for general users. It is essential that system managers perform the following steps before enabling ODS-5: o Review all ODS-5 restrictions. o Understand the support levels for different OpenVMS applications. o Segregate applications that do not support ODS-5 or have not been tested with ODS-5 names or volumes. NOTE It is recommended that you enable ODS-5 disks in a homogeneous OpenVMS Version 7.2 (and later) Alpha cluster only.
3.1 - Mixed-Version Support
Users on OpenVMS Alpha Version 7.2 (and later) systems can take advantage of Extended File Specifications capabilities. In contrast, systems running prior versions of OpenVMS cannot mount ODS-5 volumes, correctly handle extended file names, or even see extended file names. The following topics describe support on OpenVMS Version 7.2 (and later) and on prior versions of OpenVMS in a mixed-version cluster. Users on OpenVMS Alpha Version 7.2 (and later) Systems Users on OpenVMS Alpha Version 7.2 and later systems can continue to access pre-Version 7.2 files and directories; for example, they can do all of the following: o Create and access deep directory structures on ODS-2 volumes. o Read a BACKUP saveset created on an earlier version of OpenVMS. o 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 on pre-Version 7.2 Systems On mixed-version clusters, some restrictions exist. Users on a version of OpenVMS prior to Version 7.2: o 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. o 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.
3.2 - Mixed-Architecture Support
All Extended File Specifications capabilities are available on OpenVMS Alpha Version 7.2 and later systems. Current ODS-2 volume and file management functions remain the same on both VAX and Alpha Version 7.2 (and later) systems; however, extended file naming and parsing are not available on VAX systems. The following topics 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 (and later) clusters, the following Extended File Specifications capabilities are available on OpenVMS Version 7.2 (and later) VAX systems: o Ability to mount an ODS-5 volume o Ability to write and manage ODS-2-compliant files on an ODS-5 volume o See only \pISO_LATIN\.??? or \pUNICODE\.??? when accessing an ODS-5 file specification BACKUP Limitations In a mixed architecture cluster, 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.
3.3 - Network Support
Although Extended File Specifications is intended to provide enhanced file naming capabilities to Advanced Server for OpenVMS 7.2 Version 7.2 for OpenVMS Version 7.2, network access with ODS-5 volumes and extended file names is currently being tested. The length of an extended file specification that can be passed over the network using DECnet is restricted to a maximum of 255 bytes.
3.4 - Application Support
OpenVMS applications should be evaluated and tested to determine whether they function correctly when Extended File Specifications is enabled. The OpenVMS System Manager's Manual, Volume 1: Essentials contains guidelines for evaluating applications, and the Guide to OpenVMS File Applications contains details about the technical aspects of Extended File Specifications that can affect the behavior of an application.
3.5 - User Support
When you enable ODS-5 volumes on an OpenVMS cluster, you should make users aware of the following characteristics: o Extended file names caooonot be used on ODS-2 volumes. o Case is determined by the first instance of an extended file name. o There are special rules for case preservation and case blindness when using extended file names. o Some system utilities and DCL commands have a /STYLE qualifier to control the display of file names. o Error messages can vary when different parse style are used. o Extended file names are not visible from a VAX system. The OpenVMS System Manager's Manual, Volume 1: Essentials contains information for setting user's expectations of Extended File Specifications.
|4 - Impact|
The main goal of Extended File Specifications is to provide extended file naming capabilities, while also: o Maintaining high reliability, scalability, and availability o Maintaining the traditional (ODS-2) serial file interoperation capabilities o Causing the least possible amount of change for layered products and applications However, 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 following guidelines and description of changes in the base operating system will help you determine the level of impact on your OpenVMS environment.
4.1 - Support Guidelines
Under Extended File Specifications, 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: o Internal knowledge of the file system, including knowledge of: The data layout on disk The contents of file headers The contents of directory files o File parsing tailored to a particular on-disk structure. o Assumptions about the syntax of file specifications, such as the placement of delimiters and legal characters. o Assumptions about the case of file specifications. Mixed and lowercase file specifications will not be converted to uppercase, which can affect string matching operations. o Assumptions that file specifications are identical between RMS and the file system. NOTE 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.
4.2 - RMS Changes
To support Extended File Specifications, the Record Management Services (RMS) have been enhanced to provide the following functions through existing interfaces: o Support for a wider range of characters in a file name, extension, and directory o Access to file specifications with extended characters o Support for directory structures deeper than eight levels o Access to file specifications longer than 255 bytes through the NAM block with some restrictions in functionality o Access and complete specification of file specifications longer than 255 bytes by callers who are aware of the new naming characteristics through a new interface (NAML block)
4. 2.1 - Extended File Names
With ODS-5 enabled, RMS can manipulate filenames and subdirectory specifications of up to 255 8-bit or 16-bit characters in length. RMS can handle a total path name 512 8-bit or 16-bit characters in length. Prior to OpenVMS Alpha Version 7.2, the NAM block interface could pass file specifications of up to 255 bytes each (including the resultant file specification). The following topics describe the changes that allow for passing longer file specifications and that provide compatibility with applications using the NAM block interface prior to this release.
4. 2.2 - Additional Character Sets
With ODS-5, RMS supports access to files and directories whose names contain arbitrary 8-bit characters, except for the C0 control set (hex 00 through 1F) and the following characters: Double quotation marks (") Asterisk (*) Backslash (\) Colon (:) Left and right angle brackets (< >) Slash (/) Question mark (?) Vertical bar (|) Note that this explicitly includes both the C1 character set (hex 80-9F) as well as graphical and other characters between 9F and FF. This allows the entire ISO Latin-1 character set (with the 7-bit character exclusions noted above) and any defined Unicode character.
4. 2.3 - Deeply Nested Directories
Under Extended File Specifications on Alpha, RMS supports deep nesting of up to 255 directories, with the restriction that the total directory specification must be no longer than 512 8-bit or 16-bit characters. The deep nesting of directories is also supported on ODS-2 disks.
4.3 - File System (XQP) Changes
The following Files-11 Extended QIO Processor (XQP) file system enhancements are offered under Extended File Specifications through the $QIO interface. Note that in some cases, XQP file format rules may differ from those that apply to other system services that accept file names, such as those provided by RMS. o The current restrictions on the format and content of file names have been modified, specifically: - The 39.39 file name length restriction was removed to allow longer file names, up to 236 8-bit characters or 117 16-bit characters - The use of characters from the ISO Latin-1 multinational character set is supported in file specifications - Support for the entry and storage of file and directory specifications in Unicode.
4.4 - DCL Commands and Utilities
In DCL commands, you can select either of the following styles for parsing file specifications: o Traditional filenames are allowed on both ODS-2 and ODS-5 volumes. o Extended filenames are allowed on ODS-5 but not on ODS-2 volumes. Some OpenVMS commands and utilities have new qualifiers to control the interpretation and display of file specifications. NOTE DCL lexical functions use the DEC-Multinational character set, which is different from the ISOLatin-1 character set used for file names on an ODS-5 disk. This can lead to unexpected results if, for example, you use the DCL function F$EDIT to upcase a filename. Some DCL commands and OpenVMS utilities have been specifically modified to take advantage of all the features of extended file names. These utilities and commands accept and handle extended file specifications without error and without modifying their expected case. Other DCL commands and OpenVMS utilities have had little or no modification to take advantage of extended file names. These utilities and commands are expected to handle most of the attributes of extended file specifications (such as new characters and deep directory structures) correctly. Extended File Specifications Support fully defines the different levels of support for extended file names provided by DCL commands and OpenVMS utilities in OpenVMS Version 7.2 and later. The following DCL commands and OpenVMS utilities provide full support for extended file names: ANALYZE /AUDIT ANALYZE /DISK ANALYZE /RMS BACKUP CONVERT CONVERT /RECLAIM COPY CREATE /DIRECTORY DELETE DIRECTORY DUMP EDIT /ACL EXCHANGE /NETWORK FDL PURGE RECOVER/RMS RENAME SEARCH SET SECURITY SYSMAN TYPE The following table lists the new features in DCL to support Extended File Specifications. DCL Command New Features COPY Added new qualifier, /STYLE, with new keywords, EXPANDED and CONDENSED DELETE Added new qualifier, /STYLE, with new keywords, EXPANDED and CONDENSED DIRECTORY Added the following items: o Qualifier, /STYLE, with new keywords, EXPANDED and CONDENSED o Display item to /FULL to display Client Attributes DUMP Added the following items: o Display item to /DIRECTORY to display Name type attribute o Display item to /HEADER to display new attributes o Qualifier, /STYLE, with new keywords, EXPANDED and CONDENSED EXCHANGE NETWORK Added new qualifier, /STYLE, with new keywords, EXPANDED and CONDENSED F$FILE_ATTRIBUTES Added new item codes: FILE_LENGTH_HINT, Lexical VERLIMIT, DIRECTORY F$GETDVI Lexical Added new type to the ACPTYPE item code. F$GETJPI Lexical Added new item codes: PARSE_STYLE_PERM and PARSE_STYLE_IMAGE INITIALIZE Added a new qualifier: /STRUCTURE=5 device-name[:] volume-label PRINT Added new qualifier, /STYLE, with new keywords, EXPANDED and CONDENSED PURGE Added new qualifier, /STYLE, with new keywords, EXPANDED and CONDENSED RENAME Added new qualifier, /STYLE, with new keywords, EXPANDED and CONDENSED SEARCH Added new qualifier, /STYLE, with new keywords, EXPANDED and CONDENSED SET ACL Added new qualifier, /STYLE, with new keywords, EXPANDED and CONDENSED SET DEFAULT Updated the following items: o Modified the directory-spec parameter to accept ODS-5-compliant file specifications. SET DIRECTORY Added new qualifier, /STYLE, with new keywords, EXPANDED and CONDENSED SET FILE Added new qualifier, /STYLE, with new keywords, EXPANDED and CONDENSED SET PROCESS Added a new qualifier: /PARSE_ STYLE=(keyword), where keywords are TRADITIONAL and EXTENDED. SET SECURITY Added new qualifier, /STYLE, with new keywords, EXPANDED and CONDENSED SET VOLUME Added a new qualifier: /STRUCTURE_LEVEL=5 SHOW DEVICE/FULL Updated the display information to show the disk structure level. SUBMIT Added new qualifier, /STYLE, with new keywords, EXPANDED and CONDENSED TYPE Added new qualifier, /STYLE, with new keywords, EXPANDED and CONDENSED For detailed information about the enhancements made to the OpenVMS operating system and utilities in support of Extended File Specifications, see the OpenVMS DCL Dictionary: A-M, the OpenVMS DCL Dictionary: N-Z, and the OpenVMS Utility Routines Manual.
4.5 - DCL Command Parameters
Command procedures that use file names as parameters can produce different results in an ODS-5 environment. See DCL Command Parameters for more information about using ODS-5 style names in DCL command procedures.
4.6 - System Services Changes
The following system services have been modified or added to support Extended File Specifications: o New services: - $SET_PROCESS_PROPERTIESW - $CVT_FILENAME o Changed services: - $CREPRC - $GETJPI - $SETDDIR