The system, capable of handling up to five million transactions a day and being upgraded, was tested by 20 brokerages in April and May.

The tests checked out 80 percent of technical situations that could arise and the results were positive, an FPT spokesperson said Tuesday.

From now until June 25 the system would be tested on a full scale with all 73 brokerages involved before trading migrates to it in early July, he added.

On Tuesday the exchange made an unprecedented move of shutting down trading after the morning session due to an overload that threatened the system’s integrity.

Trading surged to a record VND21.76 trillion ($945 million) in the morning alone, or 85 percent of the previous day’s value.

Since the figure was unprecedented, the system gave out warnings, HoSE CEO Le Hai Tra told VnExpress.

"We saw a risk of a system crash which could affect trading in the coming days, " he said, adding that suspending trade after half a day was done to protect investors, he said.

The bourse is set to test a new system developed by the Korea Exchange from the middle of this month and switch to it by the end of the year.

HoSE’s trading system, which has remained mostly unchanged for the last 20 years, has been overwhelmed as people flock to it amid a slump in interest rates on bank deposits.