Setting maximum heap size in java

How to Increase Heap Size in Java Virtual Machine?

There are two types of memory stack memory and heap memory. All the dynamic allocations go into heap memory and the rest of the static allocations and variables allocations go into stack memory. Whenever a java program is executed in the java virtual machine it uses the heap memory to manage the data. Task Engine runs on JVM (Java Virtual Machine). Hierarchy is pictorially shown below.

So now coming onto heap memory, the heap is a location in memory used by the Java Virtual Machine (JVM). The Java Virtual Machine has a heap that is shared among all Java Virtual Machine threads. The heap is the run-time data area from which memory for all class instances and arrays is allocated. The heap is created on a virtual machine start-up. Heap storage for objects is reclaimed by an automatic storage management system (known as a garbage collector); objects are never explicitly reallocated. The Java Virtual Machine assumes no particular type of automatic storage management system, and the storage management technique may be chosen according to the implementer’s system requirements. The heap may be of a fixed size or may be expanded as required by the computation and may be contracted if a larger heap becomes unnecessary. The memory for the heap does not need to be contiguous.

A Java Virtual Machine implementation may provide the programmer or the user control over the initial size of the heap, as well as, if the heap can be dynamically expanded or contracted, control over the maximum and minimum heap size. The following exceptional condition is associated with the heap whenever a computation requires more heap than can be made available by the automatic storage management system, the Java Virtual Machine throws an OutOfMemoryError.

By default, the JVM heap size is 1GB, which is usually enough to accommodate the data used by Task Engine. However, larger heap size may be required under some circumstances, for example, when the average size of the parameters in a task is very large. Under these circumstances, the following log item is recorded in Task Engine log files. If this log item appears regularly, you need to increase the heap size.

Now the question arises of how to increase the heap size of memory. So a common solution to it Now in order to change/increase the JVM heap size is made possible by using command-line options.

-Xms : To set an initial java heap size -Xmx : To set maximum java heap size -Xss : To set the Java thread stack size -Xmn : For setting the size of young generation, rest of the space goes for old generation

Procedure: To increase the Application Server JVM heap size

1. Log in to the Application Server Administration Server.
2. Navigate to the JVM options.
3. Edit the -Xmx256m option.
4. This option sets the JVM heap size.
5. Set the -Xmx256m option to a higher value, such as Xmx1024m.
6. Save the new setting.

Note:

The process to change the heap size of the Web Server is the same you just need to log in in Web Server Administration Server. After that process is the same. It is good practice for big production projects to set the minimum -Xms and maximum -Xmx heap sizes to the same value. For efficient garbage collection, the -Xmn value should be lower than the -Xmx value. Heap size does not determine the amount of memory your process uses.

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How to Increase Heap Size in Java Virtual Machine?

There are two types of memory stack memory and heap memory. All the dynamic allocations go into heap memory and the rest of the static allocations and variables allocations go into stack memory. Whenever a java program is executed in the java virtual machine it uses the heap memory to manage the data. Task Engine runs on JVM (Java Virtual Machine). Hierarchy is pictorially shown below.

So now coming onto heap memory, the heap is a location in memory used by the Java Virtual Machine (JVM). The Java Virtual Machine has a heap that is shared among all Java Virtual Machine threads. The heap is the run-time data area from which memory for all class instances and arrays is allocated. The heap is created on a virtual machine start-up. Heap storage for objects is reclaimed by an automatic storage management system (known as a garbage collector); objects are never explicitly reallocated. The Java Virtual Machine assumes no particular type of automatic storage management system, and the storage management technique may be chosen according to the implementer’s system requirements. The heap may be of a fixed size or may be expanded as required by the computation and may be contracted if a larger heap becomes unnecessary. The memory for the heap does not need to be contiguous.

A Java Virtual Machine implementation may provide the programmer or the user control over the initial size of the heap, as well as, if the heap can be dynamically expanded or contracted, control over the maximum and minimum heap size. The following exceptional condition is associated with the heap whenever a computation requires more heap than can be made available by the automatic storage management system, the Java Virtual Machine throws an OutOfMemoryError.

By default, the JVM heap size is 1GB, which is usually enough to accommodate the data used by Task Engine. However, larger heap size may be required under some circumstances, for example, when the average size of the parameters in a task is very large. Under these circumstances, the following log item is recorded in Task Engine log files. If this log item appears regularly, you need to increase the heap size.

Now the question arises of how to increase the heap size of memory. So a common solution to it Now in order to change/increase the JVM heap size is made possible by using command-line options.

-Xms : To set an initial java heap size -Xmx : To set maximum java heap size -Xss : To set the Java thread stack size -Xmn : For setting the size of young generation, rest of the space goes for old generation

Procedure: To increase the Application Server JVM heap size

1. Log in to the Application Server Administration Server.
2. Navigate to the JVM options.
3. Edit the -Xmx256m option.
4. This option sets the JVM heap size.
5. Set the -Xmx256m option to a higher value, such as Xmx1024m.
6. Save the new setting.

Note:

The process to change the heap size of the Web Server is the same you just need to log in in Web Server Administration Server. After that process is the same. It is good practice for big production projects to set the minimum -Xms and maximum -Xmx heap sizes to the same value. For efficient garbage collection, the -Xmn value should be lower than the -Xmx value. Heap size does not determine the amount of memory your process uses.

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Increase Heap Space in Java

1. Increase Java Heap Size Using Command Line
2. Increase Java Heap Size in an Integrated Development Environment (IDE)

In Java, Heap Space is mainly used for garbage collection and allocating memory to objects.

A default Heap space is allocated when installing the JVM on our machine, but it can vary. The following points show how we can increase the heap size using two ways in Java.

Increase Java Heap Size Using Command Line

The first method to increase the heap size in Java is to use the command line to run the commands that override the default Java Heap Space. We follow the below two steps.

Step 1: Check the Default Maximum Heap Size in Java

Before we change the size of the heap in Java, we must know the default maximum heap size allocated to the JVM. To do that we use the code Runtime.getRuntime().maxMemory() that returns the maximum heap size in bytes.

In the program, we get the maximum heap space in bytes and convert it to a more readable format like megabytes or gigabytes. The output shows that our current default size is around 1.48 GB.

We perform this step so that we do not allocate a smaller size than the heap’s default size.

public class JavaExample   public static void main(String[] args)    double maxHeapSize = Runtime.getRuntime().maxMemory();  String sizeInReadableForm;   double kbSize = maxHeapSize / 1024;  double mbSize = kbSize / 1024;  double gbSize = mbSize / 1024;   if (gbSize > 0)   sizeInReadableForm = gbSize + " GB";  > else if (mbSize > 0)   sizeInReadableForm = mbSize + " MB";  > else   sizeInReadableForm = kbSize + " KB";  >   System.out.println("Maximum Heap Size: " + sizeInReadableForm);  > > 

Maximum Heap Size: 1.48046875 GB 

Step 2: Use the Command Line to Set the Maximum Heap Size

Now that we know the maximum Java heap space, we increase it using the command line.

To get the commands that we can use to modify the heap size, we open the command line and use the command java -X that returns a whole list of commands, but we are interested in only the following two commands.

The command -Xms sets the initial and minimum heap size while the -Xms sets the maximum size; we need to use the second command.

 -Xms set initial Java heap size  -Xmx set maximum Java heap size 

In the command line, we write the following command that runs the program that we see in the first step.

We use the -Xmx2g to increase the heap size by 2GB. Notice that we write the storage unit as a single character; for example, if we want to set a 2GB heap size, we write 2g.

The output shows that the default size of around 1.4GB is now modified to 2.0GB.

Increase Java Heap Size in an Integrated Development Environment (IDE)

We can also increase Java heap space in an IDE if we run the program. Although some IDEs might have different steps to perform the task, if we follow these steps, we can modify the heap size in the majority of the IDEs.

We find the Run menu item in the menu bar.

In the Run menu item, there will be an option named Run Configurations or Edit Configurations that we have to open.

A dialog box will open to show details about the application we want to run with the configurations.

There will be two input boxes: one for the program arguments and the second for VM arguments. If there is no input box for the VM arguments, we can add them using the Modify Options button.

In the input box of the VM arguments, we write the following command to run the program with the increased heap size.

Rupam Saini is an android developer, who also works sometimes as a web developer., He likes to read books and write about various things.

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