How can I make a Query consisting Count Distinct work faster in SAP Sybase IQ?

Hi,

I am having a large data set in a table where monthly data goes up to 2 Billion Records.

It consists of 2 columns Anum and Bnum out of which I have to select Anum when a column named Direction consists of X else Bnum over which I need to further apply distinct Count.

Is there any possible way to improve the performance of the query?

As of now the CPU utilization is reaching 94% and Query is taking around 30-40 minutes to return the result.

Regards

Srujan