The Tokyo Stock Exchange may be upgraded early after its IT systems had to be shut down this week when it hit maximum capacity.

The exchange had been planning to replace the current clearing system at the end of January. The new system will increase the maximum number of executed transactions from the current 4.5 million daily to 5 million per day. However, the exchange is now considering upgrading the current system as a stop-gap measure until the end of the month, said a spokesman.

The exchange needs to perform tests to determine to what level it can be upgraded. Those tests may take place over the weekend, although a decision has yet to be made.

The early upgrade comes after the market was forced to close 20 minutes early on Wednesday after heavy trading threatened to push the clearing system past its limit. The number of cleared trades hit 4.38 million by the time it was forced to shut down at 2.40pm - the first time it's been subject to such an early close in its 57-year history.

From Thursday, a 30-minute shorter trading day was imposed to help keep volumes down. Whether an upgrade goes ahead or not, the exchange will keep operating on a shortened trading day for the foreseeable future, said Miwa.