Migrating an Environment from OpenVMS VAX to OpenVMS Alpha

This manual guides developers and system managers through migrating a computing environment from an OpenVMS VAX system to an OpenVMS Alpha system or a mixed-architecture cluster. Published in December 1995, it focuses on the similarities and differences between the OpenVMS VAX and OpenVMS Alpha operating systems, which were functionally equivalent from Version 6.2.

Key aspects covered include:

• End-User Environment: Largely consistent, with most DCL commands, editors (EVE, EDT), databases, and DECforms operating similarly. Some minor differences exist in DECwindows Motif extensions and password generation algorithms.
• System Management: While many utilities and tasks are identical, significant differences arise in I/O subsystem configuration (SYSMAN on Alpha replacing SYSGEN for device drivers), disk quota requirements for Alpha images, the obsolescence of the MONITOR POOL command due to adaptive pool management, and changes in page size (Alpha systems use larger pages, employing "pagelets" for VAX compatibility). Some features, like the Patch utility and Snapshot facility, are not supported on OpenVMS Alpha, while others, like the DECevent utility and SCSI VMSclusters, are Alpha-specific.
• Programming Environment: Core development tools like the Linker, Librarian, and Debuggers are available on both platforms. However, migration requires addressing differences stemming from Alpha's RISC architecture versus VAX's CISC architecture, especially for user-written device drivers (which can be written in C on Alpha), VAX-specific floating-point data types (Dfloat, Hfloat are not natively supported on Alpha), and vector processing capabilities. Digital provides the DECmigrate utility to help translate VAX images to Alpha.
• Networking and VMSclusters: Interoperability between VAX and Alpha nodes in networks and VMSclusters is supported. However, certain DECnet (Phase IV) features, such as Level 2 routing, DDCMP lines, and VAX P.S.I., are not supported on OpenVMS Alpha. The manual details how mixed-architecture VMSclusters function and outlines restrictions for specific features.

Digital offers various migration services and training programs to assist customers with the transition.