|
Software > OpenVMS Systems > Ask the Wizard HP OpenVMS Systemsask the wizard |
|
The Question is: We are planning to migrate a host of existing application on VAX / OpenVMS on to Alpha/OpenVMS for one of our clients. The applications are in VAX C, Cobol, Pascal. Can to refer us to the manuals we need to understand the possiblities of improving the c ode performance (Optimizing the C & Cobol) to fully utilize the capabilities of Alpha/OpenVMS. The Answer is : Your particular client likely has access to direct technical assistance from Compaq, as well as various technical and managerial and migration contacts here in OpenVMS Engineering -- please seriously consider using more formal channels for this OpenVMS Alpha migration assistance. That said... First, please move to current versions of the products (compilers, OpenVMS) on the OpenVMS VAX system. Then move to OpenVMS Alpha. This two-stage port can simplify the migration process, as it separates the compiler and OpenVMS differences from the architectural differences. Then seriously consider configuring a cluster consisting of the OpenVMS VAX system(s) and the new OpenVMS Alpha system(s) -- this greatly simplifies the operations, permitting both platforms to access the same application data and application source and system configuration files, and permitting an incremental migration. Given your client's business, it would typically work best to have these clusters set up seperately from the production environment, in order to complete and verify the port before (intentionally or otherwise) going on-line with the application in the OpenVMS Alpha environment. And as for your request for assistance in optimization, first get the code running. Then look to optimize it, if necessary -- you will have wholely new versions of the code generators, and the move from a ten year old C compiler on VAX to a current-generation C compiler on Alpha will likely see some improvements in the generated code. As your particular client is also targeting a migration to recent Alpha systems, you can also look to generate code specific to EV56 (typically) to acquire access to Alpha extensions such as byte-word instructions. (You could also generate the code for EV6, but in the experience of the OpenVMS Wizard the byte-word is often the biggest single win.) Also make CERTAIN you familiarize yourself with the differences and enhancements -- Compaq C has seen many changes since VAX C. OpenVMS has also seen many changes since your VAX C code was likely written. please see the FAQ for the basics of operating with C on OpenVMS Alpha, and for topics such as correctly setting VOTES and EXPECTED_VOTES values in your development/migration cluster. Topics 2055, 3036, and 4278 reference migration, and will be of some interest in your effort. Information on moving from VAX C to Compaq C on OpenVMS VAX is included in the Compaq C for OpenVMS VAX documentation. Other relevent information is included in the OpenVMS documentation set. And of course you may also be able access at least some of the Compaq resources available to your particular client.
|