Optimising the performance
The default settings of the Delft-FEWS program are tuned for forecasting systems. These systems generally do not have a huge amount of data and table records. However, historical databases might have millions of table records, which may slow down the performance at the user interface and also the forecasting shell servers.
It is possible to change the default memory settings and to increase the performance. The settings below can be used for the OC, the FSS and stand alone systems.
Client config.xml
The second line contains the definition for the maximum allocated memory, in this case 1500 MB. This value can simply be changed to allow for more allocated memory.
<jvmOption>-Xms512m</jvmOption> <jvmOption>-Xmx1500m</jvmOption>
The flag -Xmx specifies the maximum memory allocation, while -Xms specifies the initial (and minimum) memory allocation.
The value for -Xmx is the most significant value of the two, the value for -Xms has some influence on the startup time of the application. We recommend to set it to the same value as the value for -Xmx. The choice of -Xmx should be balanced. A too small -Xmx memory setting has a lower memory footprint on an Operating System with limited memory, but may cause OutOfMemoryErrors to appear.
When rolling out a Delft-FEWS application, it is best practice is to test the application with a low memory setting (e.g. 512M) and perform some performance tests with intensive viewing of grids first. If while using a low -Xmx setting, the application's performance becomes sluggish, it is likely that the Java garbage collection memory management process is responsible. In that case it is time to tune to a higher -Xmx setting.
For testing a configuration, -Xmx1024m is a good starting point, but -Xmx1500m is most commonly, higher numbers can be used if necessary. The final rolled out Delft-FEWS application should be able to run smoothly with the specified -Xmx value. An estimate of the required memory by Delft-FEWS configuration is provided in the About Box and may also be used as guidance for the value of -Xmx.
Verifying amount of memory configured via the About Box
To analyse the currently used amount of memory in the user interface, you can open the About box from the Help menu. There you see the next window:
In this case the allocated memory for the map is already huge.
Changes to global.properties
To increase the performance of handling time series (e.g. in graphs or spatial display) you can increase the default allocated memory for caching time series.
Therefore you should add the next line to the global.properties.
timeSeriesDefaultCacheSizeMB=100
In this example 100 MB is allocated. The default value is 10 MB.
You can also increase the allocated memory for time series that are created during task runs (at a forecasting shell). To do so you should add the next line to the global.properties.
timeSeriesTaskRunCacheSizeMB=100
In this example 100 MB is allocated. The default value is 30 MB.
Temporary time series (synchLevel 9) are written to the database when the size of the write cache is not large enough to hold them in memory. This will cause a lot of extra work for the rolling barrel later on. You can set the size of this cache in the global.properties.
timeSeriesWriteCacheSizeMB=100
In this example 100 MB is allocated. The default value is 10 MB.
