The Australian Securities Exchange (ASX) has released details of the issues it suffered on Monday that caused its market to open late and close early.
In its report [PDF], the ASX said it had an "unprecedented" hardware failure that triggered a failover procedure to its backup datacentre, and while the database completed the failover, parts of ASX Trade platform did not, and remained connected to the original primary database.
"Some parts remained connected to the original database, thinking it was operating normally," the ASX said. "ASX operators were initially unaware of this anomaly."
"The issue was identified before the normal market open and most of the consequences were manually rectified. The market was then opened at 11:30am."
Two hours later, a data inconsistency was identified that was a result of the original hardware failure, which led to ASX halting the market.
As a result of the technical issues, the Australian share market may have foregone up to AU$3.5 billion in turnover.
By the next morning, the failed hardware was replaced and the market was ready to open.
ASX said the problem encountered has not been seen before by it, or its technology vendors, and has updated its procedures to prevent it happening again.
"A detailed investigation by ASX and its technology vendors has commenced to identify why the hardware malfunction caused the failover issues," the ASX said.
"Further actions include enhanced hardware monitoring, and continued investigation with vendors to improve the resilience of the system and the orderliness of the market recovery process."
In a statement, ASX managing director and CEO Dominic Stevens said the outage was unacceptable and apologised.
"Monday's disruption was especially disappointing because of ASX's long and proud record of system reliability," Stevens said. "In seven of the last 10 years, ASX's equity trading platform has recorded 100 percent system uptime. The remaining three years recorded over 99.7 percent each."
"Over the same period, there has been an almost tenfold increase in the average number of trades processed each day."
Last month the Exchange announced for the 2016 financial year it saw underlying profit after tax grow by 5.7 percent to AU$426.2 million, with operating revenue clocking in at AU$746.3 million, up 6.5 percent.