Missing oracle driver on Jasper reports server will result in the following error.

To fix this. Copy the file ojdbc6.jar

to the

C:\jasperserver\apache-tomcat\webapps\jasperserver\WEB-INF\lib
and C:\jasperserver\apache-tomcat\lib
directories
Restart Tomcat instance and all should be good to go.
Below is the copy of the error message, that is caused by the missing oracle drives.

java.lang.Exception: 1 - oracle.jdbc.driver.OracleDriver <br></br>
    at com.jaspersoft.ireport.jasperserver.ws.WSClient.runReport(WSClient.java:403) <br></br>     at com.jaspersoft.ireport.jasperserver.ws.WSClient.runReport(WSClient.java:320) <br></br>     at com.jaspersoft.ireport.jasperserver.ReportRunner.run(ReportRunner.java:70) <br></br>     at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:572) <br></br>     at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:997)