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Fixes repair problems that can lead to data loss

HP 3000 users on support contracts can contact the HP Response Center to receive patch TIXKX62A for MPE/iX 5.0 or TIXKX62B for MPE/iX 5.5.

“If you want to do Mode 6 access on a key item linked to an INDEXED AUTO Master, you need to install TIXKX62A or TIXKX62B for 5.0 or 5.5,” said Ken Sletten, chairman of the SIGIMAGE Special Interest Group.

Without the patches, queries that do a Mode 6 backward chained read against an Auto Master fail. “We got variations depending on whether or not another application was in there first,” Sletten reported, “and whether the b-tree wildcard character was the default “@” or not. Manual Masters were apparently okay.”

The DDX repair completes a fix started in November of last year, when HP announced that customers using the feature in their IMAGE databases had lost data in some cases. HP reported that it learned dataset corruption could take place under some infrequent conditions. Seven customers reported their databases were damaged while DDX was employed. (See our story on page one of the December 1997 NewsWire.)

What happens is that during the process of dynamically expanding a dataset, another process attempts to access them. This overlap has to happen in just a fraction of a second, so the timing must be just right, or as HP database lab leader Jon Bale put it, “actually, just wrong.” Adager’s Alfredo Rego said the hazard was like having your car in the shop for a 10-minute oil change – and your teenager then borrows it while it’s still up on the speed rack. While only a handful of people have reported the bug, the potential for data loss is there for any site which uses DDX and doesn’t apply HP’s fix.