Among other things, the committee is likely to look into the implications of a recent move by the National Stock Exchange to hold a compensatory trading session on Saturday, November 28, because of the holiday on November 25. The NSE announced last Thursday that there would be no trading on November 25 because of the elections in some northern states, including Delhi.

"This is the first time that a `compensatory' approach has been accepted (for trading). We need to scrutinise the issue closely because it has implications for our attempts to bring in uniform settlements at the exchanges," explained a senior Sebi official. If compensatory trading sessions become the norm, uniform settlement cycles would be more difficult to implement.

NSE managing director RH Patil defended the move for a compensatory trading day onSaturday and said it was a rare phenomenon. Asked why the exchange had been trading for the past few Saturdays as well, he said these sessions had been organised to test the NSE's new hub at Pune. "If we test on weekdays, it could affect the regular trading schedules. Hence, we have resorted to Saturdays," said Patil.

According to sources, an internal report prepared by Price Waterhouse in 1997 had suggested that the exchange should set up a backup hub to make trading failsafe.

Meanwhile, the exchange has introduced pre-opening and post-closing trading sessions as a new initiative. "It helps in better discovery of prices," said Patil. The pre-opening session is conducted from 9.45 am to 9.55 am, and this is followed by the regular trading schedule up to 3.30 pm.

Sebi sources said the government was keen to bring about structural changes in settlement cycles in order to curb excessive speculation. Currently, speculators shift their positions from one exchange to another by taking advantage of varyingsettlement cycles. This can be squelched if all exchanges have uniform settlement periods.

The sources said that the best time to bring in uniform settlements would be when stock exchanges move towards rolling settlements. But there is no unanimity among exchanges on this.

According to members of the Mayya committee, some exchanges, led by Calcutta and Bangalore, are not in favour of uniform settlements. There is also a lack of consensus on the period of settlements.

In fact, each exchange has been insisting that its own settlement cycle is the best and well-accepted by investors and hence should be followed. The two premier exchanges, NSE and BSE, which account for over 60 per cent of the national turnover, too seem to have stuck to their guns on not shifting the cycles.

Even though the finance ministry has been pushing the market regulator to bring in rolling settlements, insiders feel that this will not happen until there trading shifts completely to the demat segment.