can I access database of RTC ? If yes, suggest me the way to access Derby database.

for Derby, my personal favorite is SQuirrel : http://squirrel-sql.sourceforge.net/
but the installation and configuration might be a bit tricky... you have to install the driver for the "Derby Embedded Client", before you can connect to the DB.
One other caveat with SQuirrel, is that it connects in an exclusive mode.  So, you can either use the SQuirrel client or have the Server running at one time.. not both..

I have heard from my peers that the DB Visualizer is pretty useful as well : http://www.dbvis.com/

hope this helps..