Flaws in IBM's DB2 database software were responsible for a chain of glitches that turned a routine hardware repair into a weeklong operational crisis, Danske Bank said Thursday in a report on an outage it suffered in March.

The Copenhagen-based bank, Denmark's largest, was replacing a defective electrical unit in an IBM Ramac Virtual Array disk storage system used for DB2 data when an electrical outage in the system halted operations at one of the bank's two IT centers. Several hours later, the system was repaired and restarted.

But the next day, March 11, the bank observed problems with batch runs of collected data being processed at the affected center, in Ejby.

"Even though the re-start of the DB2 database went normally, a combination of circumstances was creating inconsistencies in the data," the bank said in a statement posted on its Web site. "This first software error in DB2 database software had existed in all similar installations since 1997, without IBM's knowledge."

The ensuing data recovery process uncovered three more DB2 flaws. The cascading series of bugs stretched the bank's recovery time out to nearly a week. By Monday, March 17, all accumulated transactions were settled and normal operations resumed, Danske Bank said.

No data was lost, and throughout the Ejby outage the bank's other operating center, in Brabrand, continued functioning fairly normally, handling cash dispensers and self-service systems. But the IT disaster took down for several days Danske Bank's currency, securities trading and clearing operations.

An IBM representative did not immediately return calls seeking comment.

Patches for the errors are now available from IBM to all DB2 users, Danske Bank said.

The IDG News Service is a Network World affiliate.