NEW YORK (REUTERS) - Nasdaq OMX Group said the system at the centre of the Nasdaq exchange's three-hour trading halt on Aug 22 had a six minute outage on Wednesday for a small number of stock symbols, but the issue had been resolved and trading was not affected.
The Securities Information Processor (SIP), which receives all traffic on quotes and orders for Nasdaq stocks, was down between 11.35am and 11.41am Eastern time (11.35pm to 11.41pm Singapore time) for symbols from PC through SPZ, the exchange operator said in a note to traders.
While Nasdaq said trading was not affected, exchange operator Direct Edge said it temporarily halted trading in Nasdaq-listed securities ranging from PBCP through ZZZZ between 11.43am and 11.48am.
The United States (US) Securities and Exchange Commission said it was in contact with Nasdaq and monitoring developments.
The issue was not related to the Aug 22 Nasdaq outage, when a software bug and other technology issues in the Nasdaq-run system was triggered by connection problems with NYSE Euronext's Arca Exchange, a person familiar with the matter said.
In that instance, the SIP was unable to revert to a back-up system and trading was halted in all Nasdaq-listed securities, including names like Apple Inc, Google Inc, and Facebook, for three hours.
Nasdaq acknowledged on Thursday that it was ultimately responsible for the trading halt.
The latest outage was due "to hardware memory failure in a back-end server", but a back-up system successfully kicked in and the issue was resolved, Nasdaq said.
The exchange said last week it was in the process of identifying potential design changes to make the SIP more resilient "including architectural improvements, information security, disaster recovery plans and capacity parameters".
Nasdaq plans to present its initial recommendations for change to the SIP governing committee, made up of US exchanges and the Financial Industry Regulatory Authority, within the next month.
SEC chairman Mary Jo White has called a meeting with the heads of exchanges on Sept 12 to address the glitch. The meeting in part will focus on ensuring SIP technology is robust enough.