Servoy is built using Java technology and as such the memory management for Servoy is basically Java Memory management. This chapter describes the basics of Java Memory management, which will be sufficient for all but the most extensive and complex deployment scenario's.

Java Memory management introduction

The basics of Java Memory management is straight forward:

Java Memory spaces

The two most important spaces of memory that a Java process uses are the Java Heap Space and the Java Perm Space. 

Java Heap Space

The Heap Space is the main space used by Java while operating. As such this space will use the most memory. The settings related to the Java Heap Space are the following:

When the Maximum Heap Space size is too low for that is actually needed by the Java process, the following exception will be thrown: java.lang.OutOfMemoryError: Java heap space

Java Perm Space

The Perm Space is the space used by Java to store objects that are long lived. As such this space will ...... The setting related to the Java Perm Space is only the following.

When the Maximum Perm Space size is too low for that is actually needed by the Java process, the following exception will be thrown: java.lang.OutOfMemoryError: PermGen space

(warning)  The above mentioned settings are settings that can be applied when launching a Java process command-line or form a .bat/.sh script. Certain application might provide other ways to specify the same settings, for example the Service component that is part of the Servoy distribution. For more information on how to configure these settings withing Servoy, read the next paragraph.

Server Memory management

Determining the required memory

The memory consumption of a Servoy Application Server consists of the following parts:

The memory usage of the Servoy Application Server itself is limited to a couple of Mb.

For the database connections assume 2Mb per connection, so sum the Maximum Active connections settings on each configured and enabled Database Server and multiply that by 2Mb to determine the maximum memory consumption by the database connections

The memory usage for the running Servoy Clients is more difficult to obtain, as it depends on the number of running Clients, the type of the running Servoy Clients, the way the Servoy Solutions that are running are built and the way the users use the Solutions. These variables together make it difficult to provide hard numbers on how to configure the memory settings beforehand. Getting it right means monitoring and tuning.

As a starting point the following rule of thumb can be used to determine the initial settings: 

Smart Client Memory usage vs. other Servoy Client

The Smart Client runs on the client machine, not on the Servoy Application Server like the other Servoy Clients, like the Web Client, Headless Client or Batch Processor. The Smart Client is only registered with the Application Server and thus consumes far less memory on the Application Server compared to the other Servoy Clients. See Smart Client Memory management for more information on configuring the Memory settings for Smart Clients specifically.

Web Client, Headless Client & Batch processors memory usage

The memory usage of Web Clients, Headless Clients and Batch Processors depends highly on the design of the solution. While Servoy optimizes many things to keep the memory footprint as low as possible, it is logical that a simple solution showing just one form at the time has a different memory footprint than a solution that has a very complex UI, showing 20 Forms and/or different sets of data at the same time.

The memory footprint is not linear with the number of Forms a Solution contains, as Forms are instantiated on a need-to basis.

As there is no way to determine up front how much memory a Web/Headless/Batch Processor Client will use, the only way to dimension the memory correctly is by monitoring and tuning it.

For the initial dimensioning, use the following rules of thumb:

Configuring the memory settings

The setting that requires tuning based on the determined required memory for the Servoy Application Server is the Maximum Heap Space setting (Xmx). By default the Maximum Heap Space is set to 256MB withing Servoy. This setting should be changed when:

Depending on how the Servoy Application Server is started, the Memory setting need to be applied in a different location.

Auto start: wrapper.conf

When using the Service component to automatically launch the Servoy Application Server when the machine on which it is installed is booted, the memory settings for the Application Server can be configured inside {serverInstall}\application_server\service\wrapper.conf by altering the "" setting:
# Initial Java Heap Size (in MB)
# Maximum Java Heap Size (in MB)

For more information on configuring the Service component, see Running the server as a service

Manual start: servoy_server.bat/.sh

When starting the Servoy Application Server manually through {serverInstall}\application_server\servoy_server.bat/.sh, the memory settings for the Application Server can be configured inside servoy_server.bat/.sh, by altering the -Xmx value:

java -Djava.awt.headless=true -Xmx256m -Xms64m -XX:MaxPermSize=128m .....
Starting in Servoy Cluster: start_servoy_clustered.bat/.sh

When the Servoy Application Server is part of a Servoy Cluster, the memory settings can be configured in {serverInstall}\application_server\terracotta\start_servoy_clustered.bat/.sh, by altering the -Xmx value:

-Xmx256m -Xms64m -XX:MaxPermSize=128m

When specifying the -Xmx and -Xms values, the following needs to be taken into account:

  • The value can only be an integer value
  • The value needs to be places directly behind the parameter, no spaces or equal signs
  • The value needs to be post fixed with the unit: "m" or "M" for megabytes, "g" or "G" for gigabytes
  • When changing the -Xms options,  make sure that the -Xmx option has a higher value
  • Both values need to be lower than the available memory on the machine
32bit Java Memory assignment limitation

(warning)   An 32 bit JVM will allow a maximum memory assignment of 2Gb in total. In order to assign more than 2Gb of memory, a 64 bit JVM on a 64 bit OS is required.

Monitoring the Memory usage

The actual memory usage of a Servoy Application Server can be observed on the Servoy Admin page. The "Servoy Server Status" overview on the "Servoy Server Home" page displays the allocated, used and maximum values for the Heap memory and all other spaces combined (non-Heap memory).

Smart Client Memory management

Similar to the Servoy Application Server, the Servoy Smart Client is also a Java application and as such the same memory management also applies to the Smart Client.

Through the Servoy Admin page, the following settings are exposed that related to the Smart Client's memory configuration:


What is does



Sets the Initial Heap Space size



Sets the Maximum Heap Space size



optional arguments that can be send to the Smart Client's JVM

Set to "-XX:SoftRefLRUPolicyMSPerMB=3600000" by default: this setting improves performance

(info)  Within the Servoy Smart Client, the actual memory usage can be monitored through the Help > About menu item.