Bug 180189 Support in memory data set cache.
Currently, Design-Time Data Cache is stored on disks. By performance tests using ramdisk, we found that caching in physical memory can improve the performance of RunAndRender by 30%.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/executor/CacheMapManager.java
x++;
					sessionTempDir = tempRootDirStr
							+ File.separator + prefix
							+ System.currentTimeMillis( ) + cacheCounter2 + "_"
							+ x;
					sessionDirFile = new File( sessionTempDir );
				}
				sessionDirFile.mkdir( );
				
				return sessionTempDir;
			}
		}
		/**
		 * Delete folder
		 * 
		 * @param dirStr
		 */
		private void deleteDir( String dirStr )
		{
			File sessionsFolder = new File( dirStr );
			if ( !sessionsFolder.exists( ) )
				return;
			File[] sessionFiles = sessionsFolder.listFiles( );
			for ( int i = 0; i < sessionFiles.length; i++ )
				sessionFiles[i].delete( );
			sessionsFolder.delete( );
		}
	}
}