Wednesday, August 20, 2014

Oracle SQL Developer - Java version issue

Oracle SQL developer (4.2) has an issue with Java version.
If you specify some incompatible version when you first time start the app, it keeps complaining every time you start it with following error:

The suggested config change in the message is red-herring. It doesn’t actually fix the problem. Apparently we need to modify configuration file  %AppData%\sqldeveloper\product.conf to fix the problem.
The file  %AppData%\sqldeveloper\product.conf contains entry for SetJavaHome. Comment the existing entry and add an entry for a valid java version.

#SetJavaHome C:\Program Files\Java\jdk1.6.0_37
SetJavaHome C:\Java\jdk1.7.0_51

While this is a solution for the java version issue, your SQL Developer may still crash!
Best and quickest way to solve it is to delete 'SQL Developer' and 'sqldeveloper' folders in %AppData% folder and start sql developer a fresh.

Thursday, August 14, 2014

HDFS Read Caching: cache-locality

Applications using HDFS will be able to read data up to 59x faster thanks to this new feature.



A centralized cache management is added to the NameNode. NameNode instructs specific datanodes to cache specific data and datanode sends cache report periodically.

Caching is user drive. User can specify which file/directory to cache and NameNode will ask DataNodes to cache the data by piggy-backing a cache command on the DataNode heartbeat reply.


While scheduling job, DataNode where data is available in cache will be given priority (amongst other replicas) by application schedulers to take advantage of cache-locality.