Microsoft's Windows 2000 operating system may have an Achilles' heel in the form of Active Directory, according to developers working with the latest beta release.
The problem stems from the way the directory is built up. Input fields, or schemas - for example "car" or "job title" - are easily added to the system, but once there cannot be deleted.
The schemas can be disabled but will still remain cluttering the system and be visible to an administrator, said Daniel House, an IBM labs engineer working on integration of the OS with IBM software.
Disabled schemas take up less than a megabyte, and, while they provide an unnecessary distraction, do not affect a system's running. However, according to House, the problem comes when two directories are joined together - as would happen, for example, if regional offices or different companies were merged.
In the likely event of two schemas of the same name meeting, a collision would occur, which could result in one or other being lost or the process breaking down, with implications for the system's scalability.
House's findings were backed up by Gary Hein, a corporate strategist and directory expert at Novell. "The problem lies with the schema definition," he said. "Active Directory cannot remove schema extensions at the moment and this could cause a same name/different syntax conflict."
Novell's competing product, Novell Directory Services, suffered from the same problem in early versions, but was corrected in version 4.01 after 18 months' labour, Hein said.
Active Directory forms the cornerstone of Windows 2000, which is scheduled to ship early next year. But schema definition is not the only problem, according to Hein. "Active Directory cannot merge two trees [large collections of linked data]," he claimed. "You have to delete all the information in one tree and copy it into the other."
IBM's House confirmed these concerns. "Microsoft has stopped telling people about replication," he said. "It now holds secret workshops at Redmond only."
Microsoft failed to respond to requests for comment.
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