Spatial Visualization - technical tips, best practices, and news from the product team

  • August 28, 2013

Potential memory usage issue when using the new MVDEMO data set

Just want to let people know that there is a memory usage issue when viewing the new MVDEMO data set at very detailed zoom levels.  As you probably have seen already the tile layer named 'demo_map' contains a raster layer that looks like the below screenshot:

mvdemo screenshot

The issue is that the base map 'demo_map' does not stop the display of this raster layer even for map scales that are way beyond the intrinsic resolution of the original raster. As a result, if you zoom in far enough, such as at zoom level 15 or beyond, the Java JAI library used for handling the raster image will cause OutOfMemory errors in the JVM and make MapViewer unresponsive. 

There is a very simple fix that involves running the following SQL statement in the database schema where the new MVDEMO data was imported:


update user_sdo_maps

set definition=

'<?xml version="1.0" standalone="yes"?>


    <theme name="WORLD_RASTER" min_scale="1.5E18" max_scale="1000000.0"

    <theme name="THEME_DEMO_STATES" min_scale="1.5E8"
max_scale="0.0" scale_mode="RATIO"/>

    <theme name="THEME_DEMO_COUNTIES" min_scale="8500000.0"
max_scale="0.0" scale_mode="RATIO"/>

    <theme name="THEME_DEMO_HIGHWAYS_LINE" min_scale="1.0E8"
max_scale="4.5E7" scale_mode="RATIO"/>

    <theme name="THEME_DEMO_HIGHWAYS" min_scale="4.5E7"
max_scale="0.0" scale_mode="RATIO"/>

    <theme name="THEME_DEMO_BIGCITIES" min_scale="4.5E7"
max_scale="7500001.0" scale_mode="RATIO"/>

    <theme name="THEME_DEMO_CITIES" min_scale="7500000.0"
max_scale="0.0" scale_mode="RATIO"/>


  where name='DEMO_MAP';

commit; /


 The above SQL changes the max_scale value for the raster layer in the basemap 'demo_map' (which the tile layer with the same name is based on).  Note that the other tile layer, 'world_map' already has the correct max_scale value for the raster theme. 

Remember to restart MapViewer or flush its cached metadata to pick up this new definition.



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