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Java Virtual Machine Performance Tuning¶

You can tune the Java Virtual Machine (JVM) settings to make a production system more efficient.

You can configure the JVM parameters in the MI_HOME/bin/micro-integrator.bat file (on Windows) or the MI_HOME/bin/micro-integrator.sh file (on Linux/Solaris). Following are the most important JVM parameters you need to configure:

Maximum Heap Memory Allocation (Xmx) - This parameter sets the maximum heap memory allocated for the JVM. Increasing the memory allocation increases the memory available for the server, which results in increasing the maximum TPS and reducing the latency. We recommend at least 2 GB of heap memory allocation for instances.
For example, If you want to set 2 GB as the maximum heap memory size, you need to configure the parameter as follows:
```
-Xms2048m -Xmx2048m
```
Here, Xmx is the maximum memory allocation pool for a JVM. Xms is the initial memory allocation pool.
Metaspace size - In JDK 1.8.*, class metadata is stored in the native heap, and this space is called Metaspace. By default class metadata allocation is only limited by the amount of available native memory. If you need to limit the amount of native memory used for class metadata, you need to set MaxMetaspaceSize. To ensure the stability of a production system, you can set the MaxMetaspaceSize parameter to 1GB as follows:
```
-XX:MaxMetaspaceSize=1g
```

When an XML element has a large number of sub elements and the system tries to process all the sub elements, the system can become unstable due to a memory overhead. This is a security risk.

To avoid this issue, you can define a maximum level of entity substitutions that the XML parser allows in the system. You do this using the entity expansion limit as follows in the MI_HOME/bin/micro-integrator.bat file (for Windows) or the MI_HOME/bin/micro-integrator.sh file (for Linux/Solaris). The default entity expansion limit is 64000.

-DentityExpansionLimit=10000

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