OpenVMS x86-64 Migration

An industrial company migrated its OpenVMS-based application to x86-64, replacing the unsupported Sybase OpenClient with FreeTDS. The migration required updating embedded SQL and porting 300,000+ lines of code in C, C++, and Fortran. VMware-based virtualization introduced networking challenges but was successfully implemented. Debugger issues slowed testing but were resolved with engineering support. VSI teams assisted with design, migration, and system tuning.

This is a medium-complexity x86-64 migration project for an industrial customer. The core application running on OpenVMS comprises some 300,000 lines of complex code written in a variety of languages (C, C++, and Fortran), interacting with a Sybase database hosted on a Windows platform, with communication between the OpenVMS-based application and the Sybase database being achieved via the Sybase OpenClient API binary-translated from Alpha. There are additionally various other interfaces to plant equipment and monitoring infrastructure. In order to migrate the application to x86-64 and provide a supportable solution going forward the unsupported Sybase client API was replaced by the open-source FreeTDS API, and an embedded SQL pre-processor was provided that could be used in conjunction with FreeTDS in place of the Sybase embedded SQL pre-processor. Testing work is still ongoing to validate the operation of the x86-64 environment, however results of testing to date indicate have shown no major problems, with most issues found to date relating to increased sensitivity of the x86-64 environment to dubious code, such as un-initialized variables and inappropriate memory accesses. It should be noted that replacement of the Sybase OpenClient with FreeTDS was performed on OpenVMS Integrity and thoroughly tested before starting the migration to OpenVMS x86-64, thereby negating the need to make any complicated and architecturally significant changes to the application environment as part of the porting work.

VSI Application Services worked closely with the customer on the replacement of the Sybase OpenClient components with FreeTDS and helped to port the application code to OpenVMS x86-64. VSI Professional Services worked closely with the customer to design and configure the target VMware-based OpenVMS x86-64 cluster environment and to develop procedures for the migration of application data and management scripts to the new environment. The VSI services teams continue to support the customer with their testing, system tuning, and with the installation of software updates.

What technical problems did that raise?

From an application perspective, the main technical challenge was replacing the Sybase OpenClient API and embedded SQL pre-processor with FreeTDS and a custom-written embedded SQL pre-processor; however, this solution has been proven on previous projects and whilst non-trivial, this replacement was viewed as being relatively low risk, a view has been generally validated, with few problems having been encountered. It should be noted that there is an outstanding issue with reliable reporting of database deadlock errors; however, this does not impact program operation.
From an infrastructure perspective, some issues have been encountered when setting up the VMware-based virtualized OpenVMS x86-64 environment related to networking, but solutions to these problems have been found. The volume of data and operational procedures required to be transferred from the old OpenVMS Integrity environment to the new x86-64 environment is relatively low, however considerable team was spent developing automated and re-runnable processes for this transfer to make cutting over to the new x86-64 environment as efficient and reliable as possible.
Probably the most significant problem encountered to date relates to issues found with the OpenVMS debugger on OpenVMS x86-64, as the debugger is used extensively by the customer to help with both development and some testing activities. As a consequence of these issues, testing has taken longer than might otherwise have been the case. Excellent feedback from the customer has helped engineering to identify and resolve many of these issues, however there are a number of issues that are still being worked on.

What are the benefits

The primary benefit to the customer is being able to move their business-critical OpenVMS application environment to a fully supported hardware and software platform that can continue to be maintained an enhanced into the future. The ability to replace unsupported/unavailable propriety Sybase OpenClient software with a supported open-source alternative of comparable quality and performance has allowed the customer to continue to use and enhance their existing application, as opposed to having to consider other options that would likely have incurred greater cost and risk.