VAX DBMS Ported to Alpha Architecture (DBMS only)
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Alpha is DEC's new 64-bit RISC based architecture that will run Open-VMS. Alpha is the future – and VAX DBMS is there. Engineers within Digital's Database Systems Group have successfully ported DBMS to the ALPHA platform. Porting DBMS to the Alpha architecture shows Digital's commitment to its customers and to the future of DBMS. Digital took the opportunity to show off DBMS running on the Alpha platform during the recent DECUS and DECWorld events. 

The developers ported DBMS v4.3 to the Alpha platform. All features, program and user interfaces and on-disk structures remain unchanged from the VAX version of the product. DBMS is DBMS, regardless of what platform it is running on. Since the on-disk structures are consistent across platforms, it will be possible to access the same VAX DBMS database from either the VAX platform or the Alpha platform.

THE PORTING EFFORT

While "VMS is VMS," porting DBMS to the Alpha platform was by no means a "recompile and run" effort. Many portions of DBMS run in elevated processor modes and make use of several low-level VMS interfaces, thus requiring modification to run in the Alpha environment.

One of the primary goals of the porting effort was to maintain a common code-base (source code) across platforms. To do this, it was necessary to eliminate dependencies on certain VAX architectural features – requiring a significant amount of code to be rewritten. According to Digital engineers, over 99 percent of the DBMS code is now common to both platforms.

PORTING YOUR DBMS APPLICATIONS TO ALPHA

According to engineers in the Database System Group, porting customer DBMS applications from the VAX to Alpha will generally require only a recompile. Customer code generally does not make use of low-level VMS interfaces or operate in elevated processor modes. Thus, most customer ports will be very straight forward. However, to get the full benefits of the Alpha architecture, customers will have to naturally align their data structures.

DATA ALIGNMENT ISSUES

To get the best performance from the Alpha architecture, customers will want to naturally align the data structures in their programs. Naturally aligned data structures will yield performance improvements on both the VAX and Alpha architecture's. While naturally aligning data structures in the VAX environment will improve performance, doing so in the Alpha environment significantly improves performance.

NATURALLY ALIGNED DATA

Naturally aligned data, is data whose lowest addressed byte resides at an address that is an even multiple of the size of the item in bytes.

• a BYTE is naturally aligned at any address.

• a WORD is naturally aligned at an even address.

• a LONGWORD is naturally aligned at a multiple of 4.

• a QUADWORD is naturally aligned at a multiple of 8.

Many of the Alpha compilers will handle data alignment issues, or issue warnings for unaligned data. Moving customer applications to the Alpha platform will generally be a straight forward path.

TRANSLATING VAX IMAGES TO ALPHA WITH VEST

Digital is offering customers two migration paths to the Alpha platform from the VAX. The first, and usually the most straight forward, is the "recompile and run" port. However, for customers that do not have access to their application's source code, the VEST (VAX Environment Software Translator) may be able to translate their VAX images into Alpha images. Digital has been using the VEST translator for over a year internally. VEST will convert your VAX executables into Alpha executables. VEST is essentially a compiler that uses VAX/VMS images as its source code. There are two issues surrounding VEST translated images that customers must be aware of:

• Translated images will execute on the Alpha platform at roughly VAX speed – they will not be able to take advantage of the Alpha architecture.

• The ability to call privileged sharable images (such as the DBCS) is questionable for VEST translated images. The jury is still out on whether VEST will provide a valid migration path for porting your VAX DBMS applications to Alpha.

In general, customers will want to "recompile and run" their applications to gain the greatest benefit from the new Alpha architecture. However, naturally aligning data will yield significant performance improvements in the Alpha environment.

The port of DBMS to the Alpha platform is proof of Digital's strong ongoing commitment to DBMS and their customers. Alpha is Digital's architecture to move them into the next century, and DBMS will be there to support your high-performance application requirements!