Migrating an Application from OpenVMS VAX to OpenVMS Alpha

This manual guides experienced software engineers through the process of migrating applications from OpenVMS VAX systems to OpenVMS Alpha systems, including mixed-architecture clusters. It outlines a comprehensive migration strategy, beginning with evaluating the application, selecting a migration method (recompiling source code into native Alpha images or translating VAX binary images using DECmigrate/VEST and the Translated Image Environment (TIE)), setting up the migration environment, debugging, testing, and integrating the migrated application.

The document details architectural differences between VAX (CISC) and Alpha (RISC) systems, focusing on impacts related to data types (e.g., floating-point, 64-bit addressing), data alignment, memory management (page size considerations), and preserving the integrity of shared data through atomicity and synchronization. It also addresses VAX-specific coding practices, exception handling mechanisms, and crucial interoperability considerations for mixed native and translated code. The manual provides specific guidance and compatibility information for various programming languages, including Ada, C, COBOL, FORTRAN, and Pascal, as well as an overview of available Digital tools and services to assist in the migration.