LSE issues technical incident update
London Stock Exchange (LSE) today issued an update on a technical incident that occurred on October 19, 2023.
At 15:11 BST on Thursday 19 October, all instruments on Partition 3 of the LSE Order Book entered into a Halt state. This affected all instruments except for constituents of the FTSE 100 and FTSE 250 indices and International Order Book securities.
It was identified that the Halts were caused by a matching engine logic issue on Partition 3 as the mirror process did not take over as would be expected in case of a hardware issue. Further investigations identified that the root cause of the issue related to the Request For Quote (RFQ) functionality for Exchange Traded Products (ETPs).
Partition 3 was restarted to expire all open orders back to customers after the restore. This process completed just after 16:45. Given this timing, it was concluded that the closing auction for Partition 3 instruments should not be operated and that closing prices would be generated from the system based on trading up to the point of the Halt.
Closing prices for the affected instruments were disseminated just after 17:00. The closing price determination followed the standard methodology as set out on column L in 2nd tab of Business Parameters. Since there was no closing auction in impacted instruments and since all orders and quotes in affected instruments were deleted during the recovery activity, most closing prices were based on the last order book traded price on the day.
Where there was not an order book trade on the day, the closing price would revert to previous day’s closing price.
Throughout, Partitions 1 and 2 supporting FTSE 100, FTSE 250 and IOB securities continued to operate as normal and proceeded to closing auction and uncrossing successfully on Thursday 19 October.
All LSE Order Book securities opened as normal on Friday 20 October.
However, as a precaution whilst our detailed investigation continues into the root cause and remediation, RFQ functionality has been temporarily disabled in respect of all ETP securities, the only securities for which this functionality has been available.