Question: What are the query browsers for DB2 e.g Database Administrator(Data Studio), Toad for DB2 etc? I worked with them but are there more ?

Answer: 
I've recently discovered DBeaver (<http://dbeaver.jkiss.org>) and I love it.
Runs on Win and Linux (on Centos7 I just unpacked an archive and ran executable), it's open source and without need of external driver it has connected to DB2 server right away. Same for PostgreSQL and MS SQL Server. 
Not sure how it compares with other in feature set though, but user experience compared to previously used Squirrel is amazing.
I recommend the IBM data studio among the free tools. It lets you

* Manipulate(Create , modify, execute) stored procedures
* See explain plans - run performance analysis
* Let you open unlimited connections which some of the free tools doesn't let you.

Also, it's based on eclipse framework, so if you are already using eclipse its almost a breeze to learn. Toad freeware is also cool, however the freeware has a licensing limitation of max 5 per enterprise.

Also, check the [latest IBM data studio download](http://www.ibm.com/developerworks/downloads/im/data/)