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
tempDtEDir.mkdir( );
				
			}
			try
			{
				tempRootDirStr = tempDtEDir.getCanonicalPath( );
			}
			catch ( IOException e )
			{
				
			}
		}
		/**
		 * @return session temp dir
		 */
		private String createSessionTempDir( )
		{
			this.createTempRootDir( );
			final String prefix = "session_";
			
			synchronized ( cacheCounter2 )
			{
				String sessionTempDir = tempRootDirStr
						+ File.separator + prefix + System.currentTimeMillis( )
						+ cacheCounter2;
				cacheCounter2 = new Integer( cacheCounter2.intValue( ) + 1 );
				File sessionDirFile = new File( sessionTempDir );
				int x = 0;
				while ( sessionDirFile.exists( ) )
				{