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With Delft-FEWS systems getting larger and more data stored in the central database it is sometimes good to review the memory settings of your Operator Client and Forecasting Shell client components. Changing these settings to more realistic values can greatly improve the performance of your system. The default settings of the Delft-FEWS settings are tuned for medium size systems, these default settings can be changed in the root configuration files (this only applies to Delft-FEWS version 2018.02 and later). There are two files that are used for these settings:

  • clientConfig.xml (for OC, FSS and SA)
  • global.properties (for OC, FSS and SA)

Client config.xml (for Delft-FEWS version 2018.02 and later)

The clientConfig.xml file can be used for memory allocation (RAM) and disk space allocation for local cache files. The default memory setting is <jvmOption>-Xmx1024m</jvmOption>. Increased memory allocation settings need to be configured using <jvmOption></jvmOption> elements. 

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  • The Xmx is configured as 1500 MB in this example. The "java heap memory (without cache)" is the Xmx memory used; = 842 MB.  This means there is still memory left.
  • Additional to the heap memory, there is the "non heap memory" and the "native memory"; total is about 400 MB.
  • The max memory used is the Xmx + this additional memory; this is 1500 + 400 = 1.9 GbGB.
  • There is also java threads memory in use.  When more displays are opened there are also more threads and more memory is used. This is normally in the order of 50-100 MB.

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  • If you reserve more RAM than available on a VM/Computer in either Windows or Linux, the performance will drop considerably as Windows the Operating System will start swapping memory.
  • We advise to use Xms setting on linux with enough memory reserved initially so the OC/FSS will run without problems. On linux it is better to set the Xms equal to Xmx.
  • If you have more RAM on a VM it is always better to increase the Xmx. The unused heap (Xmx) will be used for temporarily caching time series info, this will increase performance.
  • Do not make the Xmx larger than 32 GB.

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