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Subject: OpenVMS Frequently Asked Questions (FAQ), Part 6/11

This article was archived around: Sun, 04 Sep 2005 20:02:25 GMT

All FAQs in Directory: dec-faq/vms
All FAQs posted in: comp.os.vms, comp.sys.dec
Source: Usenet Version

Archive-name: dec-faq/vms/part6 Posting-Frequency: quarterly Last-modified: 02 Sep 2005 Version: VMSFAQ_20050902-06.TXT
DCL Details DCL does not include support asynchronous I/O, thus a predetermined protocol or a predetermined "turn-around" command sequence must be implemented in order to avoid protocol deadlocks-cases where both tasks are trying to write or both tasks are trying to read. The task that is writing messages to the network must write (or write and read) a predetermined sequence of messages, or it must write a message that tells the reader that it can now start writing messages. (This is the essence of a basic half-duplex network protocol scheme.) __________________________________________________________ 8.9 How can I get the width setting of a terminal? $ width = f$getdvi(terminal,"DEVBUFSIZ") __________________________________________________________ 8.10 Why doesn't DCL symbol substitution work? The DCL symbol substitution processing occurs only at the DCL prompt, not within data and not within files. If you wish to perform symbol substitution in this environment, you typically write a small file containing the command(s) and data to be invoked- potentially only the data-and you then invoke the created procedure or reference the specified data. In this case, use of a file containing nolinemode commands or other techniques might be useful-you will want to ensure that the text editor you use does not attempt to use screen mode or similar, as this is not generally considered adventageous within a command procedure. Tools such as FTP have alternatives: COPY/FTP. DCL symbol substitution occurs in two passes, using the ampersand and the apostrophe. In most cases, only the apostrophe is necessary. In a few cases-such as the DCL PIPE command-you will may need to use the ampersand to get the substitution to work. The following example uses ampersand substitution to transfer the contents of the header into a logical name: $ PIPE CC/VERSION | (READ SYS$PIPE hdr ; DEFINE/JOB/NOLOG hdr &hdr ) 8-9 DCL Details A logical name (in the job logical name table; shared by all processes in the current job) was used as DCL symbols cannot be returned back out from a DCL PIPE or other spawned subprocess. For related materials, please see Section 8.1 and Section 8.11. __________________________________________________________ 8.11 How can I substitute symbols in a PIPE? Use DCL ampersand substitution, and not apostrophe substitution. $ pipe show system | search sys$input opcom | (read sys$input pid ; pid=f$element(0," ",pid) ; define/system opcom_pid &pid) $ show log opcom_pid "OPCOM_PID" = "0000020B" (LNM$SYSTEM_TABLE) __________________________________________________________ 8.12 Use of RUN/DETACH, LOGINOUT, and logical names? With a command to create a detached process such as: $ RUN/DETACHED SYS$SYSTEM:LOGINOUT /INPUT=TEMP_INPUT.COM If you are trying to use a logical name as the /INPUT, /OUTPUT or /ERROR on a RUN/DETACH command, then you must translate the logical name specifications to physical references before passing them, or the definitions must reside in a logical name table that is visible to the newly-created process. Also note that LOGINOUT only creates the SYS$LOGIN, SYS$LOGIN_DEVICE, and SYS$SCRATCH logical names if it is processing a login that is based on the contents of a SYSUAF record-without access to the associated SYSUAF record, this information is not available to LOGINOUT. (If you want to see these particular logical names created, then please specify the /AUTHORIZE qualifier on the RUN/DETACHED command.) If you do not specify LOGINOUT as the image, then there is no easy way to get these logical names. Also, any logical names that are used in the target image file specification must also be in a logical name table accessible (by default) by the newly-created 8-10 DCL Details detached process. Shared tables include the group (if the process is in the same UIC group) and the system table. (If the target process is to be in another UIC group, a suitablly privileged user or application can create the necessary logical name(s) directly in the other group logical name table.) When in doubt, create a short DCL command file as input, and use a SHOW LOGICAL and similar commands to examine the context. (And use physical device and directory references on the RUN/DETACH of the LOGINOUT image, when specifying this command file as /INPUT.) Also remember to check both security auditing and system accounting when troubleshooting problems with the RUN/DETACH. Also see Section 8.2. __________________________________________________________ 8.13 How to use escape and control characters in DCL? To write a message and then the bell character, use: $ bell[0,7] = 7 $ write sys$output "Hello''bell'" To write blinking text, use: $ esc[0,7] = 27 $ text = "Blinking Text" $ write sys$output "''esc'[5m''text'''esc'[m" Also see sections Section 11.6, Section 12.1. 8-11 _______________________________________________________ 9 Files __________________________________________________________ 9.1 How can I undelete a file? OpenVMS doesn't have an "undelete" function. However, if you are quick to write-protect the disk or if you can guarantee that no new files get created or existing files extended, your data is still on the disk and it may be possible to retrieve it. The FLORIAN tool available from various websites can potentially recover the file, see question Section 13.1 for pointers. Other alternatives here include the DFU tool, available on the OpenVMS Freeware CD-ROM distribution. If you are setting up a user environment for yourself or for others, it is quite easy to use DCL to intercept the DELETE command, using a symbol: $ DEL*ETE :== @SYS$LOGIN:MYDELETE.COM The DELETE symbol will cause the procedure to be invoked whenever the user enters the DELETE command, and it can copy the file(s) to a "trashcan" subdirectory before issuing a "real" DELETE on the files. Other procedures can retrieve the file(s) from the "trashcan" subdirectory, and can (and should) clean out the "trashcan" as appropriate. (Realize that this DELETE symbol can interfere with DELETE/GLOBAL and other similar DCL commands.) __________________________________________________________ 9.2 Why does SHOW QUOTA give a different answer than DIR/SIZE? DIRECTORY/SIZE doesn't take into account the size of file headers which are charged to your quota. Also, unless you use DIRECTORY/SIZE:ALL, you will see only the "used" size of the file, not the allocated size which is what gets charged against your quota. Also, you may have files in other directories. 9-1 Files $ DIRECTORY/SIZE=ALL/GRAND [username...] Grand total of D1 directories, F1 files, B1/B2 blocks. $ DIRECTORY/SIZZ=ALL/GRAND [-]username.DIR Grand total of 1 directory, 1 file, B3/B4 blocks. $ SHOW QUOTA User [username] has B5 blocks used, B6 available of B7 authorized and permitted overdraft of B8 blocks on disk If the user has no files in other directories and all file-headers are only 1 block, then the following should apply: B5=B2+B4+F1+1 If the diskquota has drifted out of synchronization, then the system-manager can force a quota rebuild-due to various factors, the quota file can potentially drift from the actual use over time, and a periodic rebuild can be performed at appropriate intervals. Also be aware that the DIRECTORY/SIZE command can report larger values than might otherwise be expected when used to evaluate files and/or directories that are alias links-such as the system roots on OpenVMS system disks-as the command reports a total that is cumulative over all of the files and directories examined, without regard for which ones might be alias entries and which are not. (In other words, a DIRECTORY/SIZE of an entire OpenVMS system disk will report a disk useage value larger than the (usually more accurate) value reported by the SHOW DEVICE command. This as a result of the alias entries linking each SYS$SYSDEVICE:[SYSCOMMON]SYS*.DIR directory file and the SYS$SYSDEVICE:[000000]VMS$COMMON.DIR file together.) __________________________________________________________ 9.3 How do I make sure that my data is safely written to disk? If your application must absolutely guarantee that data is available, no matter what, there's really no substitute for RMS Journaling and host- or controller- based shadowing. However, you can achieve a good degree of data integrity by issuing a SYS$FLUSH RMS call at appropriate times (if you're using RMS, that is.) If you're using a high-level language's I/O system, check 9-2 Files that language's documentation to see if you can access the RMS control blocks for the open file. In C you can use fflush followed by fsync. For details on disk bad block handling on MSCP and on SCSI disk devices, please see Ask The Wizard (ATW) topic (6926). o http://www.hp.com/go/openvms/wizard/ For additional information on the OpenVMS Ask The Wizard (ATW) area and for a pointer to the available ATW Wizard.zip archive, please see Section 3.8. __________________________________________________________ 9.4 What are the limits on file specifications and directories? A file specification has an aggregate maximum size of 255 characters (NAM$C_MAXRSS) at present, assuming ODS-2 limits and traditional DCL process parsing settings (SET PROCESS/PARSE_STYLE). The node and device specification may be up to 255 characters each- file name and file types may be up to 39 characters each. File versions are from 1 through 32767, though 0 (latest version), -0 (oldest version) and -n (n'th previous version) can be used in most contexts. A file specification may not have more than 8 directories and subdirectories or-with a rooted directory, two sets of eight are possible-and while it is possible to create subdirectories of greater depth, accessing them under ODS-2 is somewhat problematic in most cases, and thus should be avoided. Under ODS-5 with extended DCL parsing (SET PROCESS/PARSE_STYLE), the filename length limits are up around 4,095 (NAML$C_MAXRSS) characters, and directories can be around 255 levels deep. Application developers should use OpenVMS-supplied routines for parsing file specifications - this ensures that changes in what is allowable will not tend to break your application. Consider that various parts of the file specification may contain quoted strings with embedded spaces and other punctuation! Some routines of interest are SYS$FILESCAN, SYS$PARSE and LIB$TRIM_ 9-3 Files FILESPEC. For further information, see the OpenVMS Guide to File Applications. Performance of larger directory files improves (greatly) with OpenVMS V7.2 and later-operations on directory files of 128 blocks and larger were rather slower on earlier OpenVMS releases due to the smaller size of the directory cache and due to the directory I/O processing logic. For fastest directory deletions, consider a reverse deletion-delete from the last file in the directory to the first. This reversal speeds the deletion operation by avoiding unnecessary directory I/O operations as the files are deleted. Tools such as the Freeware DFU can be used for this purpose, as can various available reverse-DELETE DCL command procedures. Also see Section 5.44. __________________________________________________________ 9.5 What is the largest disk volume size OpenVMS can access? One Terabyte (TB; 2**31 blocks of 2**9 bytes; 0x07FFFFFFF blocks). 255 volumes in a volume set. The largest contiguous allocation possible for any particular file is 0x03FFFFFFF blocks. Prior to the release of V6.0, the OpenVMS file system was limited to disk volumes of 8.38 GB (2**24 blocks, 16777216 blocks) or less. On some systems, there are restrictions in the console program that limit the size of the OpenVMS system disk. Note that data disks are not affected by console program limits. For example, all members of the VAXstation 3100 series are limited to a system disk to 1.073 GB or less due to the console, though larger data disks are possible. This limit due to the SCSI drivers used by and built into the console ROM to read the OpenVMS bootstrap files, and these same drivers are also used by OpenVMS to write the system crashdump. 9-4 Files There are numerous discussions of this VAXstation 3100 in the comp.os.vms newsgroup archives. Please use Google newsgroup search to search the archives for further details, for discussions of the workarounds, and for details of the potential for a simple failed bootstrap and particularly for discussions of the potential for severe system disk corruptions on crashes. Some SCSI disks with capacities larger than 8.58 gigabytes (GB) will require the use of an OpenVMS ECO kit (eg: ALPSCSI04_062 or later; see Section 14.25 for details) for new SCSI device drivers. Failure to use this ECO can cause "rounding errors" on the SCSI disk device capacity-OpenVMS will not use nor display the full capacity of the drive-and "%sysinit-e-error mounting system device status equals 000008C4" (8C4 -> "%SYSTEM-?-FILESTRUCT, unsupported file structure level") errors during bootstrap. (One workaround for the bootstrap when the bitmap is located far into the disk is the use of INIT/INDEX=BEGIN.) The problem here involves the particular extensions and fields used for larger capacity disks within the SCSI specifications and within the various intepretations of same. For ATA (IDE) disk drives: o Versions of SYS$DQDRIVER *BEFORE* X-15 topped out at 8.455 GB. Fixed drivers (equal or greater than "X-15") were shipped in: o OpenVMS Alpha V7.2-1, and later o V7.2 UPDATE V1.0 ECO, and later o V7.1-2 UPDATE V1.0 ECO, and later o V7.1-2 UPDATE V3.0 ECO, and later o The newer SYS$DQDRIVER driver operates to disks up to 33 GB without (known) problems, and effectively works with rather larger disks (up to circa 137 GB) but is known to report an incorrect number of "cylinders" with disks above 33 GB. 9-5 Files See Section for additional ATA SYS$DQDRIVER information. Be aware that a known restriction in certain older versions of the Alpha SRM Console prevents booting most ATA (IDE) drives larger than 8.455 GB, depending on exactly where the various files are located on the volume. Updated SRM consoles for systems with SRM and ATA (IDE) drive support are (will be) available. (OpenVMS Engineering has successfully bootstrapped 20GB ATA (IDE) disks using the appropriate SRM console version.) Note All disk-related listed in this section are stated in units of "disk (base ten) gigabytes" (1 GB = 10^9 bytes) and not in units of "software (base two) gigabytes" (1 GB = 2^30; 1 GB = 1073741824.) bytes. Please see Section 14.25 for details of the nomenclature and of the units. Be aware that larger disks that are using an extension of SCSI-2- disks that are using a mode page field that the SCSI-2 specifications normally reserved for tape devices-to permit a larger disk volume size will require a SCSI driver update for OpenVMS, and this change is part of V7.1-2 and later, and also part of ALPSCSI07_062 and later. (These larger disks disks will typically report a DRVERR, or will see the volume size "rounded down".) SCSI disks larger than 16777216 blocks cira 8.455 GB (base ten); 8GB (base two) require this ECO, or require the use of OpenVMS Alpha V7.1-2 or later. Applications written in C can be limited to file sizes of two gigabytes and less, as a result of the use of longword values within C file operations, and specifically off_t. This restriction is lifted in OpenVMS V7.3-1 and later, and with the application of the C ECO kits available for specific earlier releases. The use of a longword for off_t restricts applications using native C I/O to file sizes of two gigabytes or less, or these applications must use native RMS or XQP calls for specific operations. 9-6 Files Also see Section 14.13, Section 14.25. __________________________________________________________ 9.6 What is the maximum file size, and the RMS record size limit? RMS can store individual files of a size up to the maximum supported volume size. Under OpenVMS V6.0 and later, the volume size and the RMS maximum file size limit is 2**31 * 512 bytes-one terabyte (1 TB). "Use a volume set to provide a large, homogeneous public file space. You must use a volume set to create files that are larger than a single physical disk volume. (The file system attempts to balance the load on the volume sets, for example, by creating new files on the volume that is the least full at the time.)" "You can add volumes to an existing volume set at any time. The maximum number of volumes in a volume set is 255." The RMS formats-sequential, relative, and indexed- are limited by the one terabyte maximum volume size. RMS relative files are further limited to a number of records that will fit in 32 bits-4 billion records. Sequential and indexed formats do not have a record limit. Also see Section 2.17.1, Section 14.25. __________________________________________________________ 9.7 How do I write CD-Recordable or DVD media on OpenVMS? How to create CD-R, CD-RW, DVD-R, DVD+R, DVD-RW, or DVD+RW media on OpenVMS? For information on CD and DVD optical media drives on OpenVMS, please see Section 14.29. For information on the creation of OpenVMS media and of OpenVMS bootable media, a full step-by-step sequence is documented in the OpenVMS Ask The Wizard topic (9820). An abbreviated version of the sequence is included here. 9-7 Files Recording (writing) of CD and DVD optical media requires a recording or media mastering application or tool, and both commercial and non-commercial options are available. Please see CDRECORD (both non- DVD and DVD versions are available, and at least one commercial version is available), and also see DVDwrite (commercial) or DVDRECORD (open source). A port of CDRECORD is present in OpenVMS V7.3-1 and later. o Acquire a comparatively recent SCSI-based or ATAPI (IDE) CD-R or DVD-R/RW or DVD+R/RW drive. Older drives can be very problematic, while newer drives are readily available, and are cheap and very fast, and tend to have better compliance with current standards. Use of older drives is not recommended. Related device requirements information is available in Section 14.29. o Get the most recent LDDRIVER available on the Freeware, or activate and use the LD version latent in OpenVMS Alpha V7.3-1 and V7.3-2 by loading the LD command verb (look within SYS$MANAGER:CDRECORD.COM for related details), or use the integrated LD found in OpenVMS V8.2 and later. In particular, you will want to use the current ECO kit for LDDRIVER (as available), or the version of LD distributed with V8.2. The OpenVMS V8.2 version of LDDRIVER was also kitted on Freeware V7.0 as LD071. If you are not running OpenVMS V8.2, the specified LD071 kit or later, or a current ECO with the update, you will want to upgrade, or you will want to use the DCL command: SET FILE/CACHING_ATTRIBUTES=NO_CACHING on the LD partition file. This is a workaround for an incompatibility found between older LDDRIVER versions and the XFC caching support. As an alternative to LD and LDDRIVER, you can acquire and load the VD64 package from the Freeware. o Get CDRECORD or CDWRITE or other similar recording tool. 9-8 Files CDRECORD (part of CDRTOOLS), CDWRITE, and DVDRECORD (part of DVDRTOOLS) packages (DVDRECORD is a fork of CDRECORD) are freely available, and versions of CDRECORD are available on the Freeware V6.0 distribution. ( http://www.hp.com/go/openvms/freeware/ ) An OpenVMS port of the cmcd CD audio ripper is also reportedly available. http://www.amb.org/xmcd/ Versions of CDRECORD (non-DVD) are latent in OpenVMS Alpha V7.3-1 and later. Commercial versions of CDDRECORD-with DVD capabilities-are also available for various platforms, and particularly a variant of CDRECORD known as CDRECORD-ProDVD. Beware the tool chosen: some versions and configurations of CDRECORD can record DVD media, as can the DVDRECORD package, as can the commercial DVDwrite package. Many versions of CDRECORD cannot record DVD media, including the version of CDRECORD latent within OpenVMS and the version found on Freeware V6.0; these versions cannot record DVD media. o Build the contents of the disk on the LD or VD64 device partition. o Use the chosen recording tool to record the contents of the LD or VD64 partition directly onto the optical medium. Alternatively, consider the following command on OpenVMS Alpha V7.3-1 and later: @SYS$MANAGER:CDRECORD.COM HELP While folks have had success getting PC-based CD-R/RW or DVD-R/RW or DVD+R/RW tools to work with OpenVMS partitions, it is far easier and more reliable to use the OpenVMS-based versions of these tools and directly- attached devices. If you use a Windows-based tool, you will want to specifically select its raw mode, image mode, or block-copy mode, depending on the terminology within the particular tool. The transfer mode and selections is variously refered to as a disk-at-once 9-9 Files (DAO) 2048-byte block ISO Mode 1 raw/image/block data disk recording mode. More details: Creation of CD recordable or DVD recordable media under OpenVMS typically involves one of two approaches: the use of the optional CD-R (`Scribe') capabilities available for the InfoServer or other "offline" hardware packages (PC-based packages will be included in this), or the use of a host-based package such as the CDRECORD or CDWRITE13_VMS or other utilities, including OpenVMS ports of common open- source tools made available by Dr. Eberhard Heuser- Hofmann and various others. Commercial packages and options are also available. Dr. Heuser-Hofmann has DVDwrite , a commercial package which can record DVD media. ( http://home.tiscali.de/dvd4openvms ) OpenVMS can read ODS-2, ODS-5, and ISO-9660 format CD-ROMs. (If you are very careful, you can create a dual-format CD-R; a CD-R with both ODS-2 and ISO-9660 or both ODS-5 and ISO-9660 or both.) InfoServer hardware configurations are no longer available from HP, but may potentially be acquired through other means; as used equipment. InfoServer support also has very specific CD-R recording device prerequisites, and these recording devices are no longer generally available. Packages related to the use of DVD archiving are also available, see the multi-volume capabilities of the DVDarchive/restore Freeware. http://www.geocities.com/SiliconValley/Lakes/9999/vmscdwri.html Additional information is available at the following sites: o http://www.djesys.com/vms/cdrom.html o http://www.cd-info.com/CDIC/Technology/CD-R/vms.html o http://www.faqs.org/faqs/cdrom/cd- recordable/part1/preamble.html o http://www.tmesis.com/CDrom/ 9-10 Files o http://www.tditx.com/~odsiso/ U.S. Design offers a package that includes the tools necessary to create a CD or DVD-R with either ISO-9660 or ODS-2 format, for standalone CD-R/RW, DVD-R, or DVD+R/RW drives, for recent OpenVMS versions. Details are available at: o http://www.usdesign.com/ Also see Section 9.7.2 for details on access to recorded media on older CD-ROM drives. _____________________________ 9.7.1 CD and DVD notation, terminology? CD-ROM is pre-recorded Compact Disk media, and is the original and oldest CD format. The original CD media was physically stamped, a recording process that is now largely reserved to the highest-volume media reproduction requirements. CD-R is CD Recordable, a write-once storage medium that can be read by all but the oldest of CD drives; a format which can be read and often even recorded by most CD-RW drives. CD-RW is CD ReWritable, a format which is readable by many CD drives and by most CD-R drives, and with media that can be recorded and re-recorded by CD-RW drives. CD media recording speeds are listed as multiples of 150 kilobytes per second, so a 10X drive records at 1500 kilobytes (1.5 megabytes) per second. 600 MB (70 minutes) and 700 MB (80 minutes) recording capacities are both widely available. The minutes designation is derived from the traditional audio-format recording capacity of the particular media. DVD-R/RW is the older of two common Digital Versatile Disk recording formats, and the DVD-R Recordable or DVD-RW ReWritable media can be read by many DVD drives. As with CD-R formats in older CD drives, older DVD and particularly first-generation DVD players may have problems reading this media format. 9-11 Files DVD+R/RW is the newer of the two common Digital Versatile Disk recording formats, and the DVD+R Recordable or DVD+RW ReWritable media can be read by many DVD drives. Akin to DVD-R/RW media, older and particularly first-generation DVD drives can have problems reading this media format. The DVD Plus-series drives and media tend to record faster than Minus drives, as (as of this writing) the Plus (+) drives do not require an initial media formatting pass and the Minus (-) drives do. While the appropriate Plus (+) or Minus (-) DVD raw media must be chosen for the particular DVD recorder (and DVD recording drives that are compatible with and capable of using both Plus and Minus media are available), the resulting recorded media is generally readable (playable) in all recent DVD drives and DVD players, regardless of type. (Compatibility is best within the same media-series devices of course, but be certain to verify compatibility across devices regardless of the particular device or particular recording media chosen.) Presently Plus (+) media is slightly more expensive than Minus (-), but with the prices of all CD and all DVD media continuing to consistently fall, the differences in DVD media costs are becoming irrelevent for all but the production of huge volumes of DVD media. The rated DVD recording speeds are in multiples of 1353 kilobytes per second, thus a DVD 1X drive is roughly equivalent to a CD 9X drive in I/O requirements and transfer speed. DVD drive recording speed can and does vary. DVD disk drive recording speed is limited by the rated recording speed of the media used, so the slower (and cheaper) DVD media will not record any more quickly in a faster drive. A 2.4X DVD drive loaded with 1X media will record at 1X. 9-12 Files _____________________________ 9.7.2 Use of RRD42 and other older (embossed-media) CD drives? The RRD42 series SCSI CD-ROM drive is sufficiently old that it can have problems processing CD-R and CD-RW media. Other very old CD drives can have equivalent media compatibility problems when attempting to read (much) newer CD media and newer CD media technologies. These older CD drives are generally intended for use with the so-called embossed media, rather than with non-embossed recorded (recordable) media now in common circulation. Please consider using a slightly-less-ancient CD-ROM or CD-R or CD-RW drive when working with non-embossed recorded CD media. To paraphrase one knowledgable-though deliberately nameless-storage engineer, "The RRD42 drive is just past the drooling idiot stage". _____________________________ 9.7.3 Creating Bootable OpenVMS I64 CD or DVD Media? SYS$SETBOOT? If you are creating a bootable CD or DVD media for use with OpenVMS I64, you will want to specify the SYS$SETBOOT block size of 2048, and you will also want a disk cluster factor that is a multiple of four via INITIALIZE/CLUSTER=4 (or 8, or...), or you will want to ensure that SYS$EFI.SYS and SYS$DIAGNOSTICS.SYS are aligned to a multiple of four blocks; to a 2048 byte boundary. This alignment and this blocking is only necessary for OpenVMS I64, and only when creating optical media OpenVMS I64 for bootstraps. The default 512-byte block setting used by SYS$SETBOOT is the correct and expected value for traditional disk bootstraps on OpenVMS I64 systems. Once the boot files are loaded, OpenVMS I64 operates with 512-byte blocks; as is the case with ATAPI disks on OpenVMS Alpha, all application code will only see 512-byte blocks on optical media on OpenVMS I64. 9-13 Files OpenVMS I64 V8.2 and later are expected to have a version of SYS$SETBOOT that will flag a misaligned SYS$EFI.SYS and (if present) a misaligned SYS$DIAGNOSTICS.SYS file. For information on SYS$SETBOOT and the SET BOOTBLOCK command, please see Section 14.3.9 and see the OpenVMS documentation. The purpose and intent of the SYS$SETBOOT.EXE image and the SET BOOTBLOCK command is analogous to the WRITEBOOT.EXE image on existing OpenVMS VAX and OpenVMS Alpha systems. For information on CD and DVD optical media drives on OpenVMS, please see Section 14.29. For additional related information on creating bootable OpenVMS media, please see Ask The Wizard topic (9820). __________________________________________________________ 9.8 What I/O transfer size limits exist in OpenVMS? The maximum transfer size is an attribute of the particular I/O device, controller and driver combination; there is no inherent limit imposed by OpenVMS (other than the fact that, today, byte counts and LBNs are generally limited to 32 bits). The maximum size of a device I/O request is limited by the value in UCB$L_MAXBCNT, which is set by the device driver based on various factors. (Also check the setting of the MAXBUF system parameter for buffered I/O transfers, and check the process quotas.) Currently, SCSI drivers limit I/O transfers to FE00(16) bytes, 65024 bytes (decimal). The reasons for this transfer size limitation are largely historical. Similarly, DSSI devices are limited to the same value, this for hardware-specific reasons. Transfers to HSC and HSJ device controllers via the CI are limited to 1,048,576 bytes. Client MSCP-served devices are limited to 65535 bytes-to help ensure that the I/O fragmentation processing happens on the client and not on the server system. 9-14 Files Parts of the OpenVMS I/O subsystem are optimized for data transfers less than 64KB, because (obviously) most I/O operations are (substantially) less than that. OpenVMS can handle larger transfers, if the driver and the device can handle it. Also see Section 9.4, Section 9.5. __________________________________________________________ 9.9 Can I use ODBC to connect to OpenVMS database files? Yes, you can use various available third-party packages that permit remote ODBC clients to access RMS files and various commercial databases via the network. For RMS, consider acquiring one of the packages available from EasySoft, Attunity Connect (formerly known as ISG Navigator), Oracle (DB Integrator), SolutionsIQ, OpenLink Software (OpenLink Universal Data Access), and Synergex. The unixODBC package available at http://www.unixodbc.org has variously been found to operate on OpenVMS, as well. For specific commercial databases (other than RMS, of course), contact the database vendor directly for assistance. __________________________________________________________ 9.10 If my disks are shown as VIOC Compatible, am I using XFC? Yes, you are using XFC caching. Disks that are using XFC caching use communication and coordination protocols that are compatible with the older VIOC caching implementation. With the initial implementation of XFC on OpenVMS, you can use the command SHOW MEMORY/CACHE to see no disks reported in full XFC mode; all disks shown will be listed in "VIOC Compatable Mode". If you have the OpenVMS system parameter VCC_FLAGS set to 2 and are using OpenVMS Alpha V7.3-1 or later, or are using OpenVMS Alpha V7.3 with the VMS73_XFC V2.0 ECO kit or later or with the UPDATE kits, you are using XFC. 9-15 Files Another confusion: the XFC product version is and remains V1.0 in all released configurations, please do not confuse the internal XFC product version (displayed by various commands) with the version number associated with the various ECO kit(s). XFC V1.0 does not permit volumes to enter full XFC caching, as displayed by the "Vols in Full XFC mode" portion of the DCL command SHOW MEMORY/CACHE output. __________________________________________________________ 9.11 RMS Sequential Files and Platform Portability? When working with mixed platforms, you will want to become familiar with the various RMS sequential record formats, including Variable with Fixed Control (VFC), stream, stream LF, and stream CR, among other record formats. Switching formats uses CONVERT/FDL or SET FILE/ATTRIBUTES. The former converts files, the latter resets attributes. Text editors tend to select attributes when creating new files that may or may not meet requirements. If the default attributes do not match your requirements, create a stub file, SET FILE/ATTR, then edit the existing file. (Most editors will preserve attributes on an existing file.) When working with Windows, stream is usually the best choice for sequential file operations. Stream LF is most commonly used with UNIX and C applications. Windows and UNIX tend not to be able to directly read files of "unexpected" sequential RMS record formats. VFC is a common OpenVMS format, encoding the record length into the record. It is this extra data that can cause corruption-like problems when viewed without RMS; either directly via $qio or via the file system API on other operating system platforms. You will want to look at the low-level record formats, and at the RMS and the Files and Applications documentation in the OpenVMS manuals. 9-16 Files If transfering through other platforms, use of a current version of Zip (with the "-Vv" or "-V" option) and unzip, or use of a BACKUP saveset will contain and maintain the RMS file and record attributes. (For BACKUP and its own attributes requirements, see the restoration tool.) 9-17 _______________________________________________________ 10 OpenVMS Programming Information __________________________________________________________ 10.1 Modular Programming, Facility Prefixes and Symbol Naming? Please first review the OpenVMS Programming Concepts Manual and the Guide to Modular Programming manuals. Both are available within the OpenVMS documentation set, and provide details of the expected norms for OpenVMS programs. o Learn about the facility prefix, and use a the appropriate prefix uniformly throughout all external symbols, all logical names, and all files located in shared directories. The prefix and the use of the dollar sign (<$>) and the underscore (<_>) help avoid collisions with other products. Use of the dollar sign is reserved to registered products. o Please consider use of tools such as the Freeware SDL package, and the GNM package. These permit you to generate include files and message documentation akin to that of OpenVMS, providing users of your product with a familiar environment. o For product installations, consider use of the PCSI installation utility, and provide a product-specific configuration DCL command procedure (usually SYS$MANAGER:prefix$CONFIG.COM) if configuration is required. o The product startup file is usually named SYS$STARTUP:prefix$STARTUP.COM, and the shutdown file (if needed) is usually SYS$STARTUP:prefix$SHUTDOWN.COM. OpenVMS provides a registry for facility prefixes and for MESSAGE message compiler codes. To request a prefix and a message facility code for a product you distributinng to other customer sites, send your 10-1 OpenVMS Programming Information request in a mail message addressed to product[-at- sign-]hylndr.sqp.zko.dec.com, requesting the submission form and details of the registration process. Note Please do not request facility prefixes for products that local to your business, your site, or your system. Facility prefixes and message codes and the facility registration process are intended solely for HP products and Partner Products (and yes, even OpenVMS Freeware packages) that will be distributed across multiple OpenVMS customer sites. For a list of common coding bugs, please see the remainder of this section of the FAQ and specifically Section 10.22, please also see the Ask The Wizard topic (1661), and for information on debugging an OpenVMS application, please see topic (7552). o http://www.hp.com/go/openvms/wizard/ For additional information on the OpenVMS Ask The Wizard (ATW) area and for a pointer to the available ATW Wizard.zip archive, please see Section 3.8. __________________________________________________________ 10.2 Can I have a source code example of calling...? Please use the available SEARCH command on OpenVMS, and please remember to search the available resources, including the support databases and the newsgroup archives. Please also realize that most OpenVMS system services use similar calling sequences, meaning that an example of calling sys$getjpi can be used as an example for sys$getsyi and sys$getdvi. Students: please do not expect folks to write your homework for you. As for search resources: o SEARCH SYS$EXAMPLES:*.* target o SEARCH TCPIP$EXAMPLES:*.* target o http://askq.compaq.com/ o http://www.hp.com/go/openvms/freeware/ 10-2 OpenVMS Programming Information o http://www.google.com/ OpenVMS programming documentation, including the numerous example programs found in recent versions of the OpenVMS Programming Concepts manual, is available: o http://www.hp.com/go/openvms/doc/ As for details of argument passing, most OpenVMS system services and RTL routines pass string arguments by descriptor. Languages which support native string data types create descriptors automatically; those which do not (eg., C) require that you set them up explicitly. For further details on using descriptors and particularly for using descriptors from C, please see Section 10.13. There is extensive information available on how to call OpenVMS system services and OpenVMS Run-Time Library routines, including examples in numerous languages. Among the best available references are: o Your language's User Manual o OpenVMS Programming Environment Manual o OpenVMS Programming Concepts Manual o OpenVMS Programming Interfaces: Calling a System Routine o OpenVMS Calling Standard In addition, you can also locate answers, source code examples and related discussions in the Natural Language Search Assistant (AskQ) database: o http://askq.compaq.com/ (Also see Section In this area, you will find the source code of programming examples for calls to many of the OpenVMS system services (and from various programming languages), including calls to core services sys$getjpi[w], sys$getsyi[w] and sys$qio[w], as well as source code examples for calls to many other system services and run-time library routines, and examples of 10-3 OpenVMS Programming Information one of the more difficult calling interfaces found on OpenVMS systems, that of the smg$create_menu routine. Arne Vajh°j has put together a collection of OpenVMS example programs. It can be found at: o ftp://ftp.hhs.dk/pub/vms/ Additional information and examples for OpenVMS are available via: o http://www.hp.com/go/openvms/wizard/ For additional information on the OpenVMS Ask The Wizard (ATW) area and for a pointer to the available ATW Wizard.zip archive, please see Section 3.8. and via: o http://www.hp.com/go/openvms/freeware/ __________________________________________________________ 10.3 How do I get the arguments from the command line? If you're writing a program and want to accept arguments from a foreign command, you can use LIB$GET_ FOREIGN to get the command line and parse it yourself, or if you're programming in C, use the normal argc/argv method. To write an application which uses the normal DCL verb/qualifier/parameter syntax for invocation, see the description of the CLI$ routines in the OpenVMS Callable Utility Routines Reference Manual. It is possible to write an application which can be used both ways; if a DCL verb isn't used to invoke the image, the application parses the command line itself. One way to do this is to call CLI$GET_VALUE for a required parameter. If it is not present (or you get an error), call LIB$GET_FOREIGN to get the command line and do the manual parse. See also Section 8.2. 10-4 OpenVMS Programming Information __________________________________________________________ 10.4 How do I get a formatted error message in a variable? Use the SYS$PUTMSG system service with an action routine that stores the message line(s) in the variable of your choice. Be sure the action routine returns a "false" (low bit clear) function value so that SYS$PUTMSG doesn't then try to display the message (unless you want it to.) See the description of $PUTMSG in the System Services Reference Manual for an example of using an action routine. __________________________________________________________ 10.5 How do I link against SYS$SYSTEM:SYS.STB on an Alpha system? LINK/SYSEXE is the OpenVMS Alpha equivalent of linking against SYS.STB. This links against the base image: SYS$BASE_IMAGE.EXE Also see Section 10.11, particularly for pointers to the details on shareable images and shareable image creation, and see Section 10.22 for details of inner- mode floating point requirements, of data alignment, requirements for use of /NOSYSLIB, and other related inner-mode programming details, and see Section 10.11 for image-related information. __________________________________________________________ 10.6 How do I do a SET DEFAULT from inside a program? The problem is that SYS$SETDDIR only changes the default directory - NOT the default disk. The default disk is determined by the logical SYS$DISK. If you want to change the default disk within a program, then call LIB$SET_LOGICAL to change the logical SYS$DISK. You will need to call both LIB$SET_LOGICAL and SYS$SETDDIR to change both default disk and the default directory! __________________________________________________________ 10.7 How do I turn my Fortran COMMON into a shareable image on Alpha? You need to add SYMBOL_VECTOR=(<common-name>=PSECT) to your options file. On OpenVMS VAX all OVR/REL/GBL psects were automatically exported into the shareable image's Global Symbol Table. On OpenVMS Alpha you have to tell the linker that you want this done by means 10-5 OpenVMS Programming Information of the PSECT keyword in the SYMBOL_VECTOR options file statement. This has several advantages over OpenVMS VAX. First, you don't have to worry about the address of the psect when you try to create a new, upwardly compatible version of the shareable image. Second, you can control which psects, if any, are made visible outside the shareable image. By default, COMMON PSECTs in HP Fortran for OpenVMS Alpha (as well as most other OpenVMS Alpha compilers) are NOSHR. On VAX, the default was SHR which required you to change the attribute to NOSHR if you wanted your COMMON to be in a shareable image but not write- shared by all processes on the system. If you do want write-sharing, use: CDEC$ PSECT common-name=SHR in the Fortran source code (the CDEC$ must be begin in column 1) or a linker options file PSECT_ATTR statement to set the COMMON PSECT attribute to SHR. For further information, see the Linker manual. __________________________________________________________ 10.8 How do I convert between IEEE and VAX floating data? In OpenVMS V6.1 and later, the routine CVT$CONVERT_ FLOAT is documented in the LIB$ Run-Time Library Reference Manual, and can perform floating point conversions between any two of the following floating datatypes: VAX (F,D,G,H), little-endian IEEE (single, double, quad), big-endian IEEE (single, double, quad), CRAY and IBM System\370, etc. HP Fortran (all OpenVMS platforms) has a feature which will perform automatic conversion of unformatted data during input or output. See the HP Fortran documentation for information on "non-native data in I/O" and the CONVERT= OPEN statement keyword. There are floating-point conversion source code packages available for various platforms. 10-6 OpenVMS Programming Information For further floating-point related information, see: o http://www.hhs.dk/anonymous/pub/vms/collection/ieee.zip __________________________________________________________ 10.9 How do I get the argument count in a Fortran routine? On VAX, many programmers would use a MACRO routine which accessed the AP register of the caller to get the address of the argument list and hence the argument count. This was not guaranteed to work on VAX, but usually did. However, it doesn't work at all on OpenVMS Alpha, as there is no AP register. On Alpha systems, you must use a language's built-in function to retrieve the argument count, if any. In Fortran this is IARGCOUNT, which is also available in DEC Fortran on OpenVMS VAX. Note that omitting arguments to Fortran routines is non-standard and is unsupported. It will work in many cases - read the DEC Fortran release notes for additional information. __________________________________________________________ 10.10 How do I get a unique system ID for licensing purposes? Many software developers desire to use a unique hardware ID to "lock" a given copy of their product to a specific system. Most VAX and Alpha systems do not have a unique hardware-set "system ID" that can be used for this purpose. HP OpenVMS products do not use hardware IDs in the licensing methods, as many users consider a hardware-based licensing scheme to be negative attribute when considering software purchases. HP OpenVMS uses a software-based system called the License Management Facility (LMF). This provides for software keys (Product Authorization Keys or PAKS) which support capacity and user-based license checking. HP offers an LMF PAK Generator to CSA members-see Section 2.13. For information on licensing, please see Section 12.4. 10-7 OpenVMS Programming Information However, if a hardware-based method is required, the most common method is based on an Ethernet adaptor hardware address. Sample source code for implementing this is available at: o http://www.hp.com/go/openvms/wizard/ For additional information on the OpenVMS Ask The Wizard (ATW) area and for a pointer to the available ATW Wizard.zip archive, please see Section 3.8. __________________________________________________________ 10.11 What is an executable, shareable, system or UWSS image? Executable code in OpenVMS typically resides in an image-an image is a file-the file extension is typically .EXE-that contains this code. Common types of images include executable images, shareable images, system images, and protected (UWSS) images. Executable images are programs that can be directly executed. These images can grant enhanced privileges, with an INSTALL of the image with /PRIVILEGE, or can grant enhanced access with the specification of a subsystem identifier on the ACL associated with the image. Shareable images contain code executed indirectly, these images are referenced from executable images and/or from other shareable images. These images can not grant enhanced privileges, even with the use of INSTALL with /PRIVILEGE or a subsystem identifier. These shareable images can be dynamically activated (a LINK that occurs at run-time) via the LIB$FIND_ IMAGE_SYMBOL run-time library (RTL) routine. (See `protected images' for information on `privileged shareable images'.) System images are intended to run directly on the VAX or Alpha hardware-these are normally used for the kernel code that comprises an operating system. Protected images-also refered to as User-Written System Services (UWSS), or as privileged shareable images-are similiar in some ways to a standard shareable images, but these images include a `change mode' handler, and 10-8 OpenVMS Programming Information execute in an `inner' processor mode (privileged mode; executive or kernel), and code executing in inner modes has implicit SETPRV privilege. Must be INSTALLed with /PROTECT. Note that inner-mode code has restrictions around calling library routines, around calling various system services, and around calling code located in other protected or shareable images. Loadable images and device drivers are images that can be used to add code into the OpenVMS kernel. Pseudo- device drivers are a particularly convenient way to add executable code, with associated driver-defined data structures, into the kernel. The pseudo-device driver includes the UCB and DDB data structures, and a calling interface with support for both privileged and unprivileged access to the driver code via sys$qio[w] calls. A cookbook approach to creating OpenVMS shareable images is available at the URL: o http://www.hp.com/go/openvms/wizard/ For additional information on the OpenVMS Ask The Wizard (ATW) area and for a pointer to the available ATW Wizard.zip archive, please see Section 3.8. __________________________________________________________ 10.12 How do I do a file copy from a program? There are several options available for copying files from within a program. Obvious choices include using lib$spawn(), system(), sys$sndjbc() or sys$creprc() to invoke a DCL COPY command. Other common alternatives include using the callable convert routines and the BACKUP application programming interface (V7.1 and later). 10-9 OpenVMS Programming Information __________________________________________________________ 10.13 What is a descriptor? A descriptor is a data structure that describes a string or an array. Each descriptor contains information that describes the type of the data being referenced, the size of the data, and the address of the data. It also includes a description of the storage used for the data, typically static or dynamic. Descriptors are passed by reference. The following are examples of creating and using descriptors in C, with the use of the angle brackets normally expected by the C include statements deliberately altered in deference to HTML: #include {descrip.h} #include {lib$routines.h} #include {stsdef.h} int RetStat; char TxtBuf[TXTSIZ] struct dsc$descriptor StaticDsc = { 0, DSC$K_DTYPE_T, DSC$K_CLASS_S, NULL }; struct dsc$descriptor DynDsc = { 0, DSC$K_DTYPE_T, DSC$K_CLASS_D, NULL }; int DynDscLen = 255; $DESCRIPTOR( ConstDsc, "This is a string" ); /* finish setting up a static descriptor */ StaticDsc.dsc$w_length = TXTSIZ; StaticDsc.dsc$a_pointer = (void *) TxtBuf; /* finish setting up a dynamic descriptor */ RetStat = lib$sget1_dd( &DynDscLen, &DynDsc ); if ( !$VMS_STATUS_SUCCESS( RetStat ) ) return RetStat; /* release the dynamic storage */ RetStat = lib$sfree1_dd( &DynDsc ); if (!$VMS_STATUS_SUCCESS( RetStat )) return RetStat; Static descriptors reference storage entirely under application program control, and the contents of the descriptor data structure can be modified as required (by the application). OpenVMS routines do not modify the contents of a static descriptor, nor do they alter 10-10 OpenVMS Programming Information the address or length values stored in the static descriptor. (The term "static" refers to the descriptor data structure, and not necessarily to the storage referenced by the descriptor.) Dynamic descriptors reference storage under the control of the run-time library, and the contents of a dynamic descriptor data structure-once initialized- can only be modified under control of run-time library routines. The dynamic storage referenced by the dynamic descriptor is allocated and maintained by the run-time library routines. Various OpenVMS routines do alter the contents of the descriptor data structure, changing the value for the amount and the address of the storage associated with the dynamic descriptor, as required. Routines can obviously access and alter the contents of the storage referenced by the descriptor. OpenVMS languages that include support for strings or arrays are expected to use descriptors for the particular structure. Most OpenVMS languages, such as Fortran and BASIC, use descriptors entirely transparently. Some, like DEC C, require the programmer to explicitly create and maintain the descriptor. For further information on string descriptors, see the OpenVMS Programming Concepts manual, part of the OpenVMS documentation set. Fortran defaults to passing integers by reference and characters by descriptor. The following sites discuss mixing Fortran and C source code in the same application: o http://www.hhs.dk/anonymous/pub/vms/misc/FORTRAN_C_ CALL.COM o ftp://ftp.hhs.dk/pub/vms/misc/FORTRAN_C_CALL.COM 10-11 OpenVMS Programming Information __________________________________________________________ 10.14 How do I create a process under another username? Many server processes can operate within the context of the target user using privileges, using calls such as sys$chkpro and (more commonly in this context) sys$check_access as needed to determine if access would be permitted for the specified user within the current security model. With OpenVMS V6.2 and later, the persona system services (SYS$PERSONA_*) can be used to assume the persona of the specified user-these allow the server to operate as the specified user, in a controlled fashion. The persona services can be used as a "wrapper" around a sys$creprc process creation call, as well-this will create a seperate process entirely under the assumed persona. Information on the persona system services is included in the OpenVMS V6.2 new features documentation, and in the OpenVMS V7.1 and later system services documentation. These system services exist and are supported in OpenVMS V6.2 and later releases. Typical mechanisms for creating a process under another username include: o personna services around a sys$creprc call. See above. o via DECnet task-to-task, using explicit specification of username and password, or using a DECnet proxy. This creates a network-mode job under the target user. The network-mode job might do little more than a RUN/DETACH of an image passed in via task-to-task-task-to-task communications are fully available using strictly DCL-to-DCL processing, or using a compiled language and DCL, etc.) o SUBMIT/USER, or the username argument on the sys$sndjbc call. This creates a batch-mode job under the specified username. The batch-mode job might do little more than a RUN/DETACH of an image passed in via a parameter. 10-12 OpenVMS Programming Information o the UIC argument on the sys$creprc call. This mimics the UIC of the target user, and is certainly not the prefered mechanism for this task. o Via pseudo-terminals... There are likely a few other mechanisms around... There are various tools available from DECUS and other sources that allow various forms of user impersonation, as well. These tools will require version-dependent kernel code and enhanced privileges for some of (or all of) their operations. __________________________________________________________ 10.15 Why do lib$spawn, lib$set_symbol fail in detached processes? The processing within run-time library (RTL) calls such as lib$attach, lib$disable_ctrl, lib$do_command, lib$enable_ctrl, lib$get_symbol, lib$run_program, lib$set_symbol, lib$set_logical, and lib$spawn, is dependent on and requires the presence of a command language interpreter (CLI), such as DCL. Without a CLI present in the current process, these calls will fail with a "NOCLI, no CLI present to perform function" error. Detached processes typically do not have a CLI present. In place of lib$spawn, sys$creprc can often be used. The context of the parent process (symbols and logical names) will not be propogated into the subprocess when sys$creprc is used, though when there is no CLI present in the process this (lack of) propogation is moot. To create a detached process with a CLI, you must specify LOGINOUT as the target image as discussed elsewhere in the FAQ, or only use these calls (and any other calls requiring a CLI) from images that are running in an "interactive", "batch", or "other" mode process. Also note that the lib$spawn and the C system call will fail in a CAPTIVE login environment. The lib$spawn call can be gotten to work in this environment with the specification of the TRUSTED flag. 10-13 OpenVMS Programming Information __________________________________________________________ 10.16 Where can I obtain Bliss, and the libraries and supporting files? The Bliss language compilers and documentation are available on the OpenVMS Freeware distributions. Bliss language source code that contains the following statement: LIBRARY 'SYS$LIBRARY:STARLET.L32'; or similar requires the presence of the Bliss libraries. These libraries are created on the target system using the Bliss require files, and are built using the following Bliss commands: STARLET.L32 contains the public interfaces to OpenVMS: $ BLISS /LIBRARY=SYS$COMMON:[SYSLIB]STARLET.L32 - SYS$LIBRARY:STARLET.REQ LIB.L32 contains both the public and private interfaces to OpenVMS: $ BLISS /LIBRARY=SYS$COMMON:[SYSLIB]LIB.L32 - SYS$LIBRARY:LIB.REQ+SYS$LIBRARY:STARLET.REQ The equivilent files for Bliss64 are created with: $ BLISS/A64/LIBRARY=SYS$COMMON:[SYSLIB]LIB.L64 - SYS$LIBRARY:LIB.R64+STARLET.REQ+STARLET.R64 $ BLISS/A64/LIBRARY=SYS$COMMON:[SYSLIB]STARLET.L64 - SYS$LIBRARY:STARLET.R64 Some Bliss code may also require the OpenVMS VAX architecture flags. The following is the equivilent of the Alpha ARCH_DEFS.REQ module: 10-14 OpenVMS Programming Information ! ! This is the OpenVMS VAX version of ARCH_DEFS.REQ, and ! contains the architectural definitions for conditionally ! compiling OpenVMS Bliss sources for use on VAX systems. ! (If you should encounter compilation errors here, please ! seriously consider upgrading your Bliss compiler.) ! MACRO VAXPAGE = 1%; MACRO BIGPAGE = 0%; ! MACRO VAX = ! = 1 if compiled BLISS/VAX %BLISS(BLISS32V)%; ! = 0 if not compiled BLISS/VAX MACRO EVAX = ! = 1 if compiled BLISS/E* (Obsolete, old name) (%BLISS(BLISS32E) OR %BLISS(BLISS64E))%; ! = 0 if compiled /VAX /Inn MACRO ALPHA = ! = 1 if compiled BLISS/E* (New arch name) (%BLISS(BLISS32E) OR %BLISS(BLISS64E))%; ! = 0 if compiled /VAX /Inn MACRO IA64 = ! = 1 if compiled BLISS/I* (New arch name) (%BLISS(BLISS32I) OR %BLISS(BLISS64I))%; ! = 0 if compiled /VAX or /Ann MACRO ADDRESSBITS = %BPADDR%; ! = 32 or 64 based on compiler used Some Bliss code may require the definition files for the OpenVMS older LIBRTL routine lib$tparse, or the newer lib$table_parse call: $ BLISS /LIBRARY=SYS$COMMON:[SYSLIB]TPAMAC.L32 - SYS$LIBRARY:TPAMAC.REQ __________________________________________________________ 10.17 How can I open a file for shared access? When creating a file, it is often useful to allow other applications and utilities-such as TYPE-to share read access to the file. This permits you to examine the contents of a log file, for instance. A C source example that demonstrates how to do this is available in topic (2867) in the OpenVMS Ask The Wizard area: o http://www.hp.com/go/openvms/wizard/ 10-15 OpenVMS Programming Information For additional information on the OpenVMS Ask The Wizard (ATW) area and for a pointer to the available ATW Wizard.zip archive, please see Section 3.8. Depending on the environment, you may need to use C calls such as fsync and fflush, and-in specific cases- the setvbuf(_IONBF) call. __________________________________________________________ 10.18 How can I have common sources for messages, constants? Use the GNM tools on the OpenVMS Freeware to have common sources for MSG (message) files and SDML (Document) documentation files. Use the DOCUMENT command to convert the SDML documentation into the necessary formats (Text, Postscript, HTML, etc). Use the MESSAGE/SDL tool (latent in OpenVMS) to create an SDL file based on the messages. Then use the SDL tool (available on the OpenVMS Freeware) to convert the SDL file into language-specific definitions. (There is also a converter around to convert SDL into SDML, if you want to get pictures of the data structures for your documentation.) __________________________________________________________ 10.19 How do I activate the OpenVMS Debugger from an application? #include {lib$routines.h} #include {ssdef.h} #include {string.h} main() { char ascic_debug_commands[128]; char *dbgcmd = "*show calls;go;exit"; strcpy( ascic_debug_commands, dbgcmd ); ascic_debug_commands[0] = (char) strlen( dbgcmd ) - 1; lib$signal(SS$_DEBUG,1,ascic_debug_commands); return 1; } 10-16 OpenVMS Programming Information Also see Section 10.28 for another related discussion of the OpenVMS Debugger, and of a technique that uses the SS$_DEBUG signal. __________________________________________________________ 10.20 Dealing with Endian-ness? OpenVMS VAX, OpenVMS Alpha and OpenVMS I64 (as well as all Microsoft Windows implementations) all support and all use the little-endian byte ordering. Certain Alpha microprocessors and certain Intel Itanium processors can be configured to operate in big-endian and potentially in bi-endian mode. HP-UX typically operates big-endian. With little-endian byte order, the least significant byte is always the first byte; the byte at the lowest address. With big-endian byte ordering, the byte storage order in memory is dependent on the size of the data (byte, word, longword) that is being referenced. Endian-ness is a problem has been solved many times before. Some of the typical solutions include htonl/htons and ntohl/ntohs in the standard C library and the TCP/IP Services XDR (eXternal Data Representation) libraries. One of the more recently introduced network formats, and one that is seeing extensive press and marketing coverage, is XML. __________________________________________________________ 10.21 How to resolve LINK-I-DATMISCH errors? The message LINK-I-DATMISCH is informational, and indicates that the version of the specified shareable image found in the system shareable image directory does not match the version of the shareable image that was originally loaded into IMAGELIB.OLB, one of the OpenVMS libraries typically searched by the LINKER. From a privileged username, you can usually completely repair this via the following DCL command: $ LIB/REPLACE/SHARE SYS$LIBRARY:IMAGELIB.OLB SYS$SHARE:LIBRTL.EXE This command assumes that the shareable image that was found in the SYS$SHARE: area is valid and upward- compatiable, and that the image has simply replaced an older version without also updating IMAGELIB. 10-17 OpenVMS Programming Information __________________________________________________________ 10.22 HP C and other OpenVMS C Programming Considerations? VAX C V3.2 was released for OpenVMS VAX systems in 1991. DEC C V4.0 replaced VAX C V3.2 in 1993 as the HP C compiler for OpenVMS VAX systems. HP C is the ANSI C compiler for OpenVMS Alpha systems. VAX C predates the ANSI C standards, and has various areas that are not compliant with ANSI C requirements. HP C is an ANSI C compiler, and can also compile most VAX C code when /STANDARD=VAXC is specified. Versions of this compiler between V3.2 and V6.5 (exclusive) were known as DEC C, DIGITAL C, and Compaq C. Both compilers can be installed at the same time on the same OpenVMS VAX system, allowing a migration from VAX C to DEC C, and allowing the same DEC C code to be used on OpenVMS VAX and OpenVMS Alpha. The system manager can choose the system default C compiler when HP C is installed on a system with VAX C, and a C programmer can explicitly select the required compiler for a any particular compilation. A current "C" license PAK allows access to both VAX C and HP C on the same OpenVMS VAX system. Various HP C versions can be installed on OpenVMS VAX V5.5-2 and later. OpenVMS VAX releases such as V5.5-2 and V6.0 will require the installation of a HP C RTL kit, a kit that is included with the HP C compiler. OpenVMS VAX versions V6.1 and later do not require a seperate RTL kit, but HP C RTL ECO kits are available to resolve problems found with the C RTL on various OpenVMS releases. With HP C, for automatic resolution of the standard C library routines by the LINKER utility, use the /PREFIX qualifier, such as /PREFIX=ALL_ENTRIES. If a particular application program replaces an existing C library routine, use /PREFIX=(ALL_ENTRIES,EXCEPT=(...)). (VAX C required explicit specification of an RTL shareable image or C object library during the link.) 10-18 OpenVMS Programming Information When the /PREFIX is requested, the compiler generates a "decc$" prefix on the specified symbols. This prefix allows the LINKER to resolve the external symbols against the symbols present in the DECC$SHR library. The DECC$SHR library is included in the IMAGELIB.OLB shareable image library, and IMAGELIB is searched by default when any program (written in any language) is LINKed. Because the standard C library routine names are very likely to match application routines written in other languages, a prefix "decc$" is added to the C symbol names to assure their uniqueness; to prevent symbol naming conflicts. C programs, however, can sometimes have private libraries for various purposes, and the external routines share the same names as the library routines. (This is not recommended, but there are applications around that use this technique.) Thus the need to explicity specify whether or not the "decc$" prefix should be prepended to the external symbol names by the compiler. The qualifiers, and most (all?) with associated pragmas, that may be of interest when migrating VAX C code to HP C include: o Failure to specify the prefixing qualifier (on certain and usually older versions of C) can cause the compiler to not add the prefixes for the names of the C library routines into the references placed in the object module, which can in turn cause problems resolving the external symbols in the library when the object code is linked: /PREFIX=ALL_ENTRIES o Some VAX C programs erroneously write to the string literals. By default, HP C does not allow the constants to change. /ASSUME=WRITABLE_STRING_LITERALS o Enables sharing ("shr") of globals and of extern variables. HP C sets externs as non-shareable ("noshr"), VAX C as "shr". /SHARE_GLOBALS 10-19 OpenVMS Programming Information o VAX C assumes common block model for external linkages. /EXTERN_MODE=COMMON_BLOCK o Refers to the padding placed between member elements within a struct. Disabling member alignment packs the data more tightly into memory, but this packaging has performance implications, both on OpenVMS VAX and particularly on OpenVMS Alpha systems. /[NO]MEMBER_ALIGNMENT o Enable all manner of useful compiler diagnostics: /WARN=ENABLE=(LEVEL4,QUESTCODE)/STANDARD=PORT/ACCEPT=NOVAXC_KEYWORDS You can disable extraneous diagnostics with the following: #ifdef __DECC #pragma message save #pragma message disable /* insert message tag here */ #endif Permit structure members to be naturally aligned whenever possible, and avoid using /NOMEMBER_ ALIGNMENT. If you need to disable member alignment, use the equivilent #pragma to designate the specific structures. The alignment of structure members normally only comes into play with specific unaligned data structures-such as the sys$creprc quota itemlist- and with data structures that are using data that was organized by a system using byte or other non-member alignment. Versions of HP C such as V6.0 include the capability to extract the contents of the standard header libraries into directories such as SYS$SYSROOT:[DECC$LIB...], and provide various logical names that can be defined to control library searches. With HP C versions such as V6.0, the default operations of the compiler match the expectations of most OpenVMS programmers, without requiring any definitions of site-specific library- related logical names. (And logical names left from 10-20 ---------------------------- #include <rtfaq.h> ----------------------------- For additional, please see the OpenVMS FAQ -- www.hp.com/go/openvms/faq --------------------------- pure personal opinion --------------------------- Hoff (Stephen) Hoffman OpenVMS Engineering hoff[at]hp.com