By Rik Turner
IBM is considering bringing Linux to the S/390. According to Doug Nielson, a consultant on high-end systems for IBM UK Ltd, a native Linux S/390 implementation is one of three courses IBM is considering a means of taking its S/390 strategy forward, and a decision is expected within 18 months.
Big Blue actually has a number of options open to it when it comes to developing its mainframe Unix business. Its own OS/390 operating system is, in many respects, already a Unix variant, having already achieved PPG 95 endorsement, and the OS can now run both Unix applications and legacy S/390 applications. However, in future, says Nielson, IBM sees some important choices ahead for Unix on the mainframe.
One alternative currently under consideration is to continue to develop S/390’s Unix personality towards the Unix 98 standard, Nielson said. The present interface is for Unix 95, but XPG has already released the latest 98, and IBM is evaluating its advantages.
A second route, however, might be to endow S/390 with the same interfaces as the Monterey operating system, essentially the future of IX. And the third course might mean Linux. But, Nielson was quick to add, at the moment the open source operating system still isn’t for mission-critical applications and so is unlikely to make an early debut on S/390.
Even so, IBM is already considering how, if Linux does make the mainframe grade, it might best be brought on board. The favored approach, according to Nielson, would be a native port to the hardware, as Amdahl has already done to its PCM kit, but IBM is also thinking of running Linux as a guest operating system under the auspices of a VM hypervisor.
As for the 64-bit question currently occupying the Unix community, Nielson said the S/390 will eventually go 64-bit, though it is in a more comfortable position than its 32-bit competitors because thanks to the nature of the architecture, S/390 is 32-bit but with 44-bit addressing. Nonetheless, with an increasing number of Unix applications (from Oracle, SAP and IBM’s own DB2 operating system business) coming onto the market in 64-bit versions, he said that he expects S/390 to go 64-bit in the next two to three years.
