VMS / OpenVMS Operating RTL System Services for x86 RedHat and SUSE Linux

VX/RT is a collection of over 900 VMS / OpenVMS system service calls for Linux and Windows. All of the VMS / OpenVMS API's are written in native C and C++ for Linux and Windows. They are call compatible, take the same arguments and return the same results. Even errors codes are mapped from Linux and Windows errors code to VMS / OpenVMS error codes.  For example SYS$OPEN takes a pointer to a FAB and would return RMS$_FNF (98964) if the fine is not found. The FAB requires no changes and most of the fields are supported (obviously some field such as number of extents make no sense on some target systems).

It is also these same API's that cause the greatest difficulty when moving those applications to an operating system that does not support the equivalent API's. Sector7 designed VX/RT to enable the application to be ported with the minimum number of code changes. To this end, the VX/RT API's accept VMS file specifications and return VMS return codes. For example SYS$OPEN takes a pointer to a FAB and would return RMS$_FNF (98964) if the file is not found. The FAB requires no changes and most of the fields are supported (obviously some field such as number of extents make no sense on some target systems).

Sector7 provides an ODBC interface to VX/RMS allowing concurrent data retrieval in a client server mode from Windows based systems and applications. VX/RMS is accessible from the standard SYS$ interface and provides full support for FAB, RAB, NAM and XABs. VX/RMS also includes a full FDL$ API set with the corresponding FDL command line programs (ANALYZE/RMS CONVERT/FDL).

VX/RT includes a number of user data conversion routines. The primary problem when moving data between VMS and other architectures is that the internal data representation is different, not only in byte ordering but also the default floating point format on most OPEN systems is IEEE488 and VMS is DFLOAT. Sector7 provides VX/DataX that will convert RMS data records to any machine architecture. Variable format records are handled by Sector7 data scripting language.

The VMS / OpenVMS API's to the RMS subsystem are VMS / OpenVMS compliant. Most take the form SYS$XXXX({Rdb/Fab}, AST Success, AST Error) FABDEF, RABDEF, NAMDEF, XAMDEF etc are the same structure as VMS / OpenVMS and the same definitions from STARLET can be used.

VX/RT supports full VMS / OpenVMS AST's. AST generation and delivery performs exactly the same way as on VMS / OpenVMS. AST's supported: USER, SUPERVISER, EXECUTIVE and KERNEL mode. AST's generated from Asynchronous I/O, TIMERS, are delivered in the same way that they are delivered under VMS / OpenVMS. VX/RT supports VMS / OpenVMS timers, allowing multiple timers and SCHEDULE and CANCEL with AST delivery. VMS / OpenVMS DATE/TIME is fully supported in a QUADWORD based upon the number of microseconds since the MJD (Modified Julian Date) of Nov 17, 1858.

LIB$ADD_TIMES, LIB$CVT_FROM_INTERNAL_TIME, LIB$CVT_TO_INTERNAL_TIME, LIB$CVT_VECTIM,, LIB$CVTF_TO_INTERNAL_TIME, LIB$DATE_TIME, LIB$DAY, LIB$DAY_OF_WEEK, LIB$EDIV
LIB$MULT_DELTA_TIME, LIB$SUB_TIMES, LIB$SUBX, LIB$VECTIM, SYS$ASCTIM, SYS$BINTIM, SYS$GETTIM, SYS$NUMTIM

Most applications are invoked through a DCL script or call DCL from within the program to perform functions. VX/DCL is a complete DCL for open systems which allows both "standard" command line usage together with programmable API's from the user applications ( LIB$SPAWN, LIB$DO_COMMAND, LIB$GET_SYMBOL, LIB$GET_SYMBOL ).VX/DCL is responsible for the maintenance of the LOGICAL TABLES and the SYMBOL tables. Programs report completion status backs VX/DCL via IPC mechanisms. VX/DCL allows full VMS file specs to be used for operations and will execute "on the fly" conversion to the pen system specification. VX/DCL supports an interface to VX/JSP , which provides Batch and PRINT services through a VMS queue management system implemented on open systems.

COMMAND LINE INTERPRETER (CLI)

Many applications make use of the very powerful DEC COMMAND LINE INTERPRETER. Commands formats are created and the CLI will scan the input command line and apply the syntax rules programmed into the definition file (CLD). Sector7 provides VX/CLI , which combines a command line definition compiler and a command line interpreter.

PRINT AND BATCH QUEUES

VX/RT includes support for VMS / OpenVMS BATCH and PRINT Queue's. Over 100 DCL commands and modifiers which translate down to SYS$SNDJBC(W) and SYS$GETQUI(W) commands are implemented

VX/RT supports a VMS compliant logical manager allowing user definable tables and logical inheritance classes for sub processes. User mode and kernel mode logical are supported and persistence rules adhered to. In addition to the standard logical management, Sector7 has extended the logical subsystem to allow logicals to be accessed and set from Linux style API's All Sector7 language translators accept VMS file specs and logical names as input to file I/O routines. VX/RT supports the full range of logical name tables, logicals and logical search lists.

SYMBOLS

VXRT also supports VMS / OpenVMS symbols. Unlike Linux environment variables, VX/RT symbols talk via IPC to VX/DCL which stores the symbol values ensuring that symbols can be set in a program and retrieved in a different program or in the VX/DCL CLI. Symbols set in a program via SYS$SET_SYMBOL are available to VX/DCL as soon as they are set. The equivalent "symbol" in Linux, when set via putenv() is ONLY available to the program and not carried back to the controlling shell.

VMS / OpenVMS memory management API's have been faithfully reproduced in the Sector7 library system. PAGED based allocation (VM_PAGE), ZONE based allocation (VM_ZONE) and GLOBAL PSECT ($CRMPSC etc) functionality is implemented. Certain restrictions apply to mapping global sections due to the memory architecture of the target systems, generally mapping of I/O ports to memory addresses is NOT supported. GLOBAL sections can be mapped into A Linux/Windows 3GL (C, C++, COBOL, BASIC, Fortran, PASCAL) to provide the same logical functions as on VMS / OpenVMS 3GL's.

EVENT FLAGS

Most VMS applications, especially those using asynchronous and inter-process communication I/O will use VMS event flags to synchronize code fragments. VMS event flags differ in many ways from Linux or NT semaphores. Sector7 has implemented full VMS event flag functionality allowing the application to make full use of LOCAL and GLOBAL clustered event flags. All of the VMS APIs for controlling access to event flags are fully supported. Event flags are set on asynchronous and asynchronous operations.