Normally in a scatter chart when we are showing the tooltip, we are seeing only Y-Axis values but making some alternations we can include both the x-axis and y-axis values in the tooltip.
For this you need to alter scatter.pcxml file.
you have to update this file in two locations.
1.\OracleBI\web\app\res\s_<stylename>\popbin
2.\OracleBI\oc4j_bi\j2ee\home\applications\analytics\analytics\res\s_<stylename>\popbin
you have to update this file in two locations.
1.\OracleBI\web\app\res\s_<stylename>\popbin
2.\OracleBI\oc4j_bi\j2ee\home\applications\analytics\analytics\res\s_<stylename>\popbin
in this scatter.pcxml file
in between <Graph> tag search for Datalabels tag,here you have to identify formatstring value like this:
in between <Graph> tag search for Datalabels tag,here you have to identify formatstring value like this:
<DataLabels Font=’Size:9;Style:Bold;’ TransparentBackground=’False’ BGColor=’#FFFFFFcd’FormatString=’%_XVALUE
%_YVALUE’ />
It will give you both X and Y values at your Tooltip. Where 
 is for new line character in xml.
I tried this example using paint.rpd’s Region, Brand and dollars and this is screen shot for X and Y values at tool tip.