IBM's move to formally support Linux on the S/390 mainframe gives users an industrial-strength platform for running applications based on the open-source operating system, analysts and users said.
But the traditional capacity-based licensing schemes associated with mainframe software, along with Linux's immaturity in enterprise environments, could slow the take-up, they added.
"It is an extremely interesting move because the S/390 offers a range of possibilities that doesn't exist on other platforms," said Dan Kaberon, parallel sysplex manager at Hewitt Associates in Illinois, one of the nation's largest outsourcers of corporate benefits packages.
But "it will be more effective for users to put [Linux applications] on cheaper RISC-based processors than on a mainframe until IBM can fix its current software pricing scheme," said Carl Greiner, an analyst at Meta Group.
Under capacity-based pricing schemes, users pay for software according to the size of the system it's running on - generally the larger the system, the more costly it is to runsoftware.
"We have an offer that enables customers to develop and run Linux applications ina dedicated workspace without impacting their current S/390 software charges," said an IBM spokesman.
IBM last week said it will offer a full range of support services for Linux on the S/390.
Under the initiative, Linux for S/390 will be sold by Nurnberg, Germany-based SuSE Inc. and TurboLinux Inc. in San Francisco, both of which are Linux vendors.
IBM Global Services, the company's professional services unit, will work in collaboration with SuSE and TurboLinux to offer technical support and middleware integration services.
Last week's announcement formalizes Linux support on S/390 systems. IBM has been making free Linux code available on the mainframe platform since January, but users who take the free software don't get service and support.
In its announcement, IBM said the fact that more than 2,100 mainframe users have downloaded the code since January prompted its decision to provide formal Linux service and support on the S/390.
The ability to run Linux jobs on mainframes, in proximity to traditional big-iron workloads and databases, should make applications for the operating system easier to manage and increase their scalability and performance, said Mike Kahn, an analyst at The Clipper Group Inc. in Wellesley, Massachusetts.
One example is OS/390's VM/ESA guest support, under which users can run "thousands of Linux virtual machines on a single piece of hardware," Kaberon said.
But Linux still isn't as robust as other Unix versions - such as IBM's AIX, Sun Microsystems Inc.'s Solaris or Hewlett-Packard Co.'s HP-UX - which will limit user interest in running Linux on mainframes, Greiner said.
"It may or may not be useful in 2000," agreed Kaberon. "But it is going to become more and more useful over the next several years.... We are just going to watch this very carefully."
IBM is planning a lineup of mainframe software for Linux that includes middleware, databases and management software. Most of the software will become available in the fourth quarter.