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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 first (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. When running on Windows 32 bits and the -Xmx value is set too high for 32 bits (>1500M), it reduces the available memory for native drivers (e.g. firebird) and the Operator Client / ConfigManager may suffer from lack of native memory which can cause unstable behaviour. For testing a configuration, 512M is a good starting point, but 1024M is the most commonly used value for end-users running 32-bits. For 64-bits mode, higher numbers can be used if necessary. The final roll rolled out of the Delft-FEWS application should be able to run smoothly with the specified -Xmx value.
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