Using Bitmap Access Plans on Regular B-tree Indexes

Hi. I have a 10 million row table with b-tree indexes with one column each on columns Column_A, and Column_B. This is an OLTP table.

The SQL that needs to be tuned is causing a B-Tree to Bitmap conversion that is taking 100 seconds.

Using columns A and B together, I can get down to 2% of the table.

I'm considering adding Column_B to the INDEX with Column_A in order to speed up the query. I don't want to adversely affect the performance of other queries that may need to do a B-Tree to Bitmap conversion.

Can a B-Tree to Bitmap conversion be executed on a COMPOSITE INDEX?

Are there other things I should consider before adding the additional column?

Thanks,

G