The older IBM G4, G5 and G6 31-bit mainframes running OS/390 2.10 are still used at more than 1,000 sites worldwide, according to analyst firm Gartner. Up to half of the 120 sites in the UK have yet to upgrade to 64-bit zSeries hardware and z/OS, said Meta Group.
IBM has given users four years' notice to migrate to a 64-bit mainframe, but Gartner analyst Michael Chuba said, "Users are concerned about the move to 64-bit. A lot of their applications are 15-20 years old. They want to know what happens if something goes wrong with the migration."
The complexity of the migration may have contributed to users' reluctance to upgrade. Julie-Ann Williams, chairwoman of the mainframe special interest group at IBM user group, GuideShare Europe, said, "Migrating in-house applications onto z/OS is almost like Y2K all over again."
Phil Payne, principal at Isham Research, said, "Many users do not want to upgrade their mainframe hardware at the same time as the operating system."
IT directors who have not installed new mainframes will have to convince senior management to set aside hundreds of thousands of pounds to purchase the IBM z/OS 1.4 to ensure they eventually receive support from IBM for the migration to the 64-bit zSeries mainframe.
IBM introduced the 31-bit compatibility mode in z/OS 1.4 18 months ago to allow users to upgrade their mainframe operating system independently of the hardware. But when z/OS 1.5 ships in March, the 31-bit compatibility mode will no longer be available.
Doug Nielson, system consultant at IBM, said IBM's strategy was to move users onto a 64-bit platform before September 2004 when z/OS 1.6 ships. That version, unlike previous versions of z/OS, will only run on 64-bit zSeries hardware.
Nielson said, "It would be prudent for users to buy z/OS 1.4 before it stops shipping." He said anyone purchasing the z/OS 1.4 operating system would receive support for 64-bit migration until 2007, when z/OS 1.4 support officially expires.
One user running IBM G4 and G5 series mainframes on OS/390 2.10 in a utilities company said, "If I do not have the software, I cannot stay within IBM's support policy. I need the zSeries hardware for the migration path to z/OS."
Another user, at an agricultural equipment manufacturer, said he was using an IBM G4 mainframe with OS/390 2.10 to run several applications, including payroll. Again, he faced the problem of migrating both hardware and the operating system simultaneously.
"We will have to order z/OS 1.4 before March 2004 to ensure we get support for our 64-bit migration," he said.
The migration onto 64-bit could prove costly and he was concerned that some third-party mainframe software suppliers may charge an upgrade fee.
GuideShare Europe is running a special interest group meeting on 20 January to look at the 64-bit transition for mainframe users.