Alter row-store table to column-store doesn`t work

Hey guys

I`m developing a web servlet with JPA and I wanted to change my column-store table (created by default) in SAP HANA database to a column-store table. I tried to do this by following the steps in this description (ALTER TABLE Example):

https://help.hana.ondemand.com/help/frameset.htm?937ca0a472bb101490cf767db0e91070.html

At this code line

ds = (DataSource) ctx.lookup("java:comp/env/jdbc/DefaultDB");

I got an error

javax.naming.NameNotFoundException: Name [DefaultDB] is not bound in this Context. Unable to find [DefaultDB].

I can`t find any solutions... Can someone help me???

Thanks in advance!