OutOfMemoryError in java in lots of detail
Contents of page >
1) Different types of java.lang.OutOfMemoryError >
Exception in thread: java.lang.OutOfMemoryError: Java heap space
Exception in thread: java.lang.OutOfMemoryError: GC Overhead limit exceeded
Exception in thread: java.lang.OutOfMemoryError: Requested array size exceeds VM limit
Exception in thread: java.lang.OutOfMemoryError: Metaspace
Exception in thread: java.lang.OutOfMemoryError: request size bytes for reason. Out of swap space?
Exception in thread: java.lang.OutOfMemoryError: Compressed class space
Exception in thread: java.lang.OutOfMemoryError: reason stack_trace_with_native_method
Out of memory:Kill process or sacrifice child
Exception in thread : java.lang.OutOfMemoryError: permgen
java.lang.OutOfMemoryError is the commonly a indication of a memory leak in java.
Now, let’s discuss all of them in detail.


Before learning in detail about OutOfMemoryError in java, we must know about JVM Heap memory (Hotspot heap structure). Let's learn about heap in just 1 minute.
JVM Heap memory (Hotspot heap structure) with diagram in java >
JVM Heap memory (Hotspot heap structure)  in java consists of following elements>
  1. Young Generation
    • 1a) Eden,
    • 1b) S0 (Survivor space 0)
    • 1c) S1 (Survivor space 1)
  2. Old Generation (Tenured)
  3. Permanent Generation.
2) Scenarios where OutOfMemoryError may be thrown >
  • Usually whenever there is insufficient space to allocate an object in the Java heap OutOfMemoryError is thrown.
  • What happens when there is insufficient space to allocate an object in the Java heap > The garbage collector is unable make some space available to accommodate a new object, and even the java heap cannot be expanded to create new object. (See how to adjust heap size using -Xms and -Xmx jvm parameters)


  • OutOfMemoryError may also be thrown when there is insufficient native memory to support the loading of a Java class.


  • OutOfMemoryError may also be thrown when an excessive amount of time is being by jvm in performing garbage collection and very little memory is being freed.
  • OutOfMemoryError exception can also be thrown by native library code when a native allocation cannot be satisfied (Example - if swap space is low).


3.1) Exception in thread thread_name java.lang.OutOfMemoryError: Java heap space in java


OutOfMemoryError : Java heap space - is thrown whenever there is insufficient space to allocate an object in the Java heap.
Is Exception in thread threadName - java.lang.OutOfMemoryError - Java heap space
Indicates memory leak?
No, this OutOfMemoryError does not necessarily means that it is memory leak.


3.2) How to solve Exception in thread thread_name java.lang.OutOfMemoryError - Java heap space in java?
You may need to increase the heap size using -Xms and -Xmx jvm parameters as a solution to this issue.
2.1) What is -Xms JVM parameter in java?
-Xms : Xms is minimum heap size which is allocated at initialization of JVM in java.


Examples of using -Xms VM (JVM) option in java >
Example1 of using -Xms VM (JVM) option in java >
java -Xms512m MyJavaProgram
It will set the minimum heap size of JVM to 512 megabytes.
2.2) What is -Xmx JVM parameter in java?
-Xmx : Xmx is the maximum heap size that JVM can use.


Examples of using -Xmx VM option in java >
Example1 of using -Xmx VM (JVM) option in java >
java -Xmx512m MyJavaProgram
It will set the maximum heap size of JVM to 512 megabytes.

Read more in detail - What are -Xms and -Xmx JVM parameters in java, and differences between them with examples
3.3) OutOfMemoryError may also be thrown in java when >
OutOfMemoryError may also be thrown when an excessive amount of time is being by jvm in performing garbage collection and very little memory is being freed.


A long lived application might be unintentionally holding references to objects and this prevents the objects from being garbage collected. Holding of objects for a long time is also a kind of memory leak in java.


Also one of the most important source of OutOfMemoryError ( Java heap space)  could be the excessive use of finalizers in the application.


What happens with the excessive use of finalizers in the application?
If a class has a finalize method, then space for object is not reclaimed at garbage collection time. Instead the objects are queued for finalization after garbage collection, finalization occurs at some later time.


3.4) How excessive use of finalizers could cause OutOfMemoryError in java?
finalizers are executed by a daemon threads. As we discussed above that finalization occurs at some later time. Holding finalizer daemon threads for long time could fill the Java heap and cause OutOfMemoryError.
3.5) Example/Program in java to generate OutOfMemoryError: Java heap space >
Before executing program pass this vm parameter in eclipse.
-Xmx5m   (Here maximum heap memory set to just 5 megabytes, so that we could easily produce OutOfMemoryError: Java heap space)
package outofmemory;
import java.util.ArrayList;
import java.util.List;
/**
*
* Write a program which could throw
* java.lang.OutOfMemoryError : Java Heap Space
*
*/
public class OutOfMemoryErrorJavaHeapSpace {
   static List<String> list=new ArrayList();
   public static void main(String[] args) {
          while(true){
                 list.add(new String("a"));   //Line 16
          }
   }
}
OUTPUT of program >
Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
   at java.util.Arrays.copyOf(Unknown Source)
   at java.util.Arrays.copyOf(Unknown Source)
   at java.util.ArrayList.grow(Unknown Source)
   at java.util.ArrayList.ensureExplicitCapacity(Unknown Source)
   at java.util.ArrayList.ensureCapacityInternal(Unknown Source)
   at java.util.ArrayList.add(Unknown Source)
   at outofmemory.OutOfMemoryErrorJavaHeapSpace.main(OutOfMemoryErrorJavaHeapSpace.java:16)
The solution is simply to increase the Xmx parameter to -Xmx512m as we discussed above.


Must read: How to set, change, increase or decrease heap size in tomcat server and eclipse to avoid OutOfMemoryError ?

>How to set or change permgen size in tomcat server, eclipse?
4.1) Exception in thread threadName - java.lang.OutOfMemoryError: GC Overhead limit exceeded in java
OutOfMemoryError: GC Overhead limit exceeded - indicates that the garbage collector is running all the time and Java program is making very slow progress.
After a GC (garbage collection), if the garbage collector is spending more than 98% of its time in doing garbage collection and if less than 2% of the java heap memory space is reclaimed, then OutOfMemoryError - GC Overhead limit exceeded - is thrown in java.


This OutOfMemoryError is generally thrown because all the live objects are not getting garbage collected properly and java heap space is not available for new objects.
4.2) How to avoid OutOfMemoryError - GC Overhead limit exceeded in java?
You must increase the heap size to avoid OutOfMemoryError - GC Overhead limit exceeded in java as a solution to this issue..


4.3) How to turn off OutOfMemoryError - GC Overhead limit exceeded in java?
You can turn it off by using VM (JVM) argument -XX:-UseGCOverheadLimit
4.4) Example/Program in java to generate OutOfMemoryError: GC Overhead limit exceeded >
Before executing program pass this vm parameter in eclipse.
-Xmx4m -XX:+UseParallelGC  (so that we could easily produce OutOfMemoryError: GC Overhead limit exceeded)
package outofmemory;
import java.util.ArrayList;
import java.util.List;
/**
*
* Write a program which could throw
* java.lang.OutOfMemoryError : GC Overhead limit exceeded
*
*/
public class OutOfMemoryErrorGCoverheadLimitExceeded {
   static List<String> list=new ArrayList();
   public static void main(String[] args) {
          while(true){
                 list.add(new String("a"));  //Line 16
          }
   }
}
OUTPUT of program >
Exception in thread "main" java.lang.OutOfMemoryError: GC overhead limit exceeded
   at outofmemory.OutOfMemoryErrorGCoverheadLimitExceeded.main(OutOfMemoryErrorGCoverheadLimitExceeded.java:16)
The solution is simply to increase the Xmx parameter to -Xmx512m as we discussed above.


5) OutOfMemoryError : unable to create new native Thread - Xss JVM option
5.1) What is java.lang.OutOfMemoryError : unable to create new native Thread ?
When JVM don’t have enough memory/space to create new thread it throws OutOfMemoryError : unable to create new native Thread.
Also read : Read in detail about : OutOfMemoryError in java
5.2) Solving OutOfMemoryError : unable to create new native Thread ?
You can resolve “java.lang.OutOfMemoryError : unable to create new native Thread” by setting the appropriate size using -Xss vm option.


Solution 1 to “java.lang.OutOfMemoryError : unable to create new native Thread”  >
Try to increase the the -Xss value so that new threads gets enough stack space.
Solution 2 to “java.lang.OutOfMemoryError : unable to create new native Thread”  >
Alternatively you could also increase the heap size available using -Xms and -Xmx options and then try to increase and set appropriate -Xss value.
5.3) How to use Using the VM (virtual machine) option ss?
We can use the VM option ss to adjust the maximum stack size.
VM option is passed using -X followed by your VM option. So, passing ss with -X forms -Xss.
Examples of using -Xss
Pass memory value you want to allocate to thread stack with -Xss.
Example1 of using -Xss >
java -Xss512m MyJavaProgram
It will set the default stack size of JVM  to 512 megabytes.
Example2 of using -Xss >
java -Xss1g MyJavaProgram
It will set the default stack size of JVM  to 1 gigabyte.
5.4) What happens if value of -Xss set is too high?
Setting excessive value of -Xss parameter could cause StackOverFlowError in java.
5.5) Program which throws java.lang.OutOfMemoryError : unable to create new native Thread
/**
*
* Write a program which could throw
* java.lang.OutOfMemoryError : unable to create new native Thread
*
*/
public class OutOfMemoryErrorUnableToCreateNewNativeThreadExample {
   public static void main(String[] args) {
          //start/spawn infinite Threads
          while(true){
                 final int i=0;
          new Thread(new Runnable(){
              public void run() {
                System.out.println(Math.random() +" ");
                  try {
                      Thread.sleep(10000000);
                  } catch(InterruptedException e) { }    
              }   
          }).start(); //When JVM don’t have enough space to create new thread it
                                 throws OutOfMemoryError : unable to create new native Thread
          }
   }
}
In the above program we are spawning infinite Threads.
In while loop we are starting threads and putting them to sleep for a long time, so that the threads don’t die. (Learn thread states in java)
After certain time JVM won’t have enough space to create new thread and throw OutOfMemoryError : unable to create new native Thread.
Note : As above program will throw  OutOfMemoryError : unable to create new native Thread. So, executing above program might make your system to hang as it will run out of memory.
Output of above >
Exception in thread "main" java.lang.OutOfMemoryError: unable to create new native thread
at java.lang.Thread.start0(Native Method)
at java.lang.Thread.start(Unknown Source)
at infiniteThreads.main(infiniteThreads.java:19)
5.6) -Xss option is also known as >
Also you must know that -Xss option is same as -XX:ThreadStackSize
5.7) Default Values of -Xss for different platforms >
For windows 32 bit its 64 KB.
For linux 32 bit its 128 KB.
For windows 64 bit its 128 KB.
For linux 64 bit its 256 KB.
For Solaris Sparc it’s 512KB.
5.8) Every thread has its own stack >
You must know that each and every thread has its own stack, which makes the methods thread-safe as well.


6.1) Exception in thread threadName - java.lang.OutOfMemoryError: Requested array size exceeds VM limit in java
OutOfMemoryError: Requested array size exceeds VM limit - indicates that the java application tried to allocate an array larger than the heap size.


6.2) Example of OutOfMemoryError - Requested array size exceeds VM limit in java >
If heap size is 512 MB, and
java application tries to allocate an array of size 1024 MB.
In this case, OutOfMemoryError - Requested array size exceeds VM - will be thrown because java application tried to allocate an array larger than the heap size.


6.3) How to avoid/solve OutOfMemoryError - Requested array size exceeds VM limit in java?
You must increase the heap size to avoid OutOfMemoryError - Requested array size exceeds VM limit.
Also, you may check the size of array which you are creating, because generally size of array shouldn’t be not that large, if size of array is more than size of java heap it may be a faulty array.
The solution is simply to increase the Xmx parameter to -Xmx512m
6.4) Example/program in java to generate OutOfMemoryError: Requested array size exceeds VM limit >
Before executing program pass this vm parameter in eclipse.
-Xmx5m   (Here maximum heap memory set to just 5 megabytes, so that we could easily produce OutOfMemoryError: Requested array size exceeds VM limit)
package outofmemory;
/**
*
* Write a program which could throw
* java.lang.OutOfMemoryError : Requested array size exceeds VM limit
*
*/
public class OutOfMemoryErrorRequestedArraySizeExceedsVMlimit {
   public static void main(String[] args) {
          Integer[] array = new Integer[10000 * 10000];  //Line 11
   }
}
OUTPUT of program >
Exception in thread "main" java.lang.OutOfMemoryError: Requested array size exceeds VM limit
   at outofmemory.OutOfMemoryErrorRequestedArraySizeExceedsVMlimit.main(OutOfMemoryErrorRequestedArraySizeExceedsVMlimit.java:11)
The solution is simply to increase the Xmx parameter to -Xmx512m as we discussed above.




7.1) Exception in thread threadName - java.lang.OutOfMemoryError: Metaspace in java
java.lang.OutOfMemoryError:Metaspace is thrown when there is no space to allocate metaspace for java class metadata.
7.2) What is Java class metadata?
Java class metadata is the JVM’s (Java virtual machine) internal presentation of Java class.
7.3) What is metaspace?
Java class metadata is allocated in native memory called metaspace.
7.4) When OutOfMemoryError: Metaspace is thrown in java?
OutOfMemoryError: Metaspace is thrown when -
  • Too many class are loaded or
  • Classes loaded very huge in size.
In this case there is no space to allocate metaspace for java class metadata.
7.5) How Metaspace to be allocated is decided in java?
Metaspace available for java class metadata is limited by VM (JVM) argument -XX:MaxMetaspaceSize,
7.6) Example of using MaxMetaSpaceSize in java >
-XX:MaxMetaspaceSize=64m
Whenever this specified metaspace becomes full and there is no further space to allocate metaspace for java class metadata OutOfMemoryError: Metaspace is thrown.


7.7) How to avoid OutOfMemoryError - Metaspace in java?
You may increase the value of metaspace by passing the above VM argument (-XX:MaxMetaspaceSize).
7.8) Tradeoff between java heap and MetaSpace in java >
MetaSpace is allocated from the same address spaces as the Java heap. Reducing the size of the Java heap will make more space available for MetaSpace. This is only a correct trade-off if there is an excess of free space in the Java heap.
7.9) Example/program in java to generate OutOfMemoryError: Metaspace >
Before executing program pass this vm parameter in eclipse.
-XX:MaxMetaspaceSize=5m  (So that we could easily produce OutOfMemoryError: Metaspace)
We will use javassist.ClassPool to create new classes.
import javassist.ClassPool;
/**
*
* Write a program which could throw
* java.lang.OutOfMemoryError : Metaspace
*
*/
public class OutOfMemoryErrorMetaspace {
   //ClassPool objects hold all the CtClasses.
   static ClassPool classPool = ClassPool.getDefault();
   public static void main(String[] args) throws Exception {
          for (int i = 0; i < 100000; i++) {
                 //makeClass method - Creates a new class (or interface) from the given class file.
                 Class clas = classPool.makeClass(
                              i + " outofmemory.OutOfMemoryErrorMetaspace ").toClass();
                 //Print name of class loaded
                 System.out.println(clas.getName());
          }
   }
}
Download Jar used in the program javassist.jar
OUTPUT of program >
0 outofmemory.OutOfMemoryErrorMetaspace
1 outofmemory.OutOfMemoryErrorMetaspace
2 outofmemory.OutOfMemoryErrorMetaspace
3 outofmemory.OutOfMemoryErrorMetaspace
4 outofmemory.OutOfMemoryErrorMetaspace
5 outofmemory.OutOfMemoryErrorMetaspace
6 outofmemory.OutOfMemoryErrorMetaspace
7 outofmemory.OutOfMemoryErrorMetaspace
8 outofmemory.OutOfMemoryErrorMetaspace
9 outofmemory.OutOfMemoryErrorMetaspace
10 outofmemory.OutOfMemoryErrorMetaspace
11 outofmemory.OutOfMemoryErrorMetaspace
12 outofmemory.OutOfMemoryErrorMetaspace
13 outofmemory.OutOfMemoryErrorMetaspace
Exception in thread "main" java.lang.OutOfMemoryError: Metaspace
So, from output we can clearly see that only 13 classes were loaded and then OutOfMemoryError: Metaspace was thrown.


The solution is simply to increase the Xmx parameter to -XX:MaxMetaspaceSize=512m as we discussed above.
For more details please read : OutOfMemoryError: Metaspace Solved
OutOfMemoryError: “request size bytes for reason. Out of swap space” indicates that allocation from the native heap failed.


8.1) What does “request size bytes for reason. Out of swap space” indicates in java?
It indicates the size (in bytes) of the request that failed and the reason for the memory request.
Usually the reason is the name of the source module reporting the allocation failure, although sometimes it is the actual reason.
8.2) What happens in OutOfMemoryError: “request size bytes for reason. Out of swap space”?
When OutOfMemoryError: “request size bytes for reason. Out of swap space” happens the
  • JVM generates a error log file which contains information about the
    • threads,
    • processess,
    • system state at the time of the crash.
8.3) How to analyze OutOfMemoryError: “request size bytes for reason. Out of swap space” in java?
You can analyze above information, heap memory and memory map to find out reason for OutOfMemoryError: “request size bytes for reason. Out of swap space”.
You can also use different OS (operating system) tools to analyze OutOfMemoryError: “request size bytes for reason. Out of swap space”.


Must read Related : How to monitor and analyze the garbage collection in 10 ways in java and Detecting and fixing memory leak in java
9.1) Cause of OutOfMemoryError: Compressed class space  in java >
If you working on 64-bit platforms a pointer to class metadata can be represented by a 32-bit offset (by using vm option UseCompressedClassPointers - This vm option is enabled by default).
If vm option is kept enabled then amount of space available for class metadata is fixed (i.e. specified by vm option)
If amount of space available for class metadata is exceeds CompressedClassSpaceSize, then java.lang.OutOfMemoryError Compressed class space is thrown.
9.2) Example of using UseCompressedClassPointers vm option in java >
-XX: CompressedClassSpaceSize=2g
It will set size of 2 gigabyte.
Now, if space available for class metadata exceeds 2 gigabyte, then java.lang.OutOfMemoryError Compressed class space is thrown.
9.3) You must also know that there different type of class metadata -
  • klass metadata (only it is stored in CompressedClassSpaceSize) and
  • other metadata (it is not stored in CompressedClassSpaceSize, it is stored in Metaspace).
For more details please read : OutOfMemoryError: Compressed class space in java
10) Exception in thread threadName : java.lang.OutOfMemoryError: reason stack_trace_with_native_method
10.1) What happens in OutOfMemoryError: reason stack_trace_with_native_method
Whenever this OutOfMemoryError is thrown >
  • a stack trace is printed
  • In this stack top frame is a native method
Then this OutOfMemoryError indicates that a native method has encountered an allocation failure.
10.2) When this OutOfMemoryError: reason stack_trace_with_native_method is detected?
In this OutOfMemoryError: “reason stack_trace_with_native_method” the allocation failure is detected in >
rather than in the JVM code.
10.3) Action you should take in case of OutOfMemoryError: reason stack_trace_with_native_method?
Use native utilities of the OperatingSystem to diagnose the issue.


10.4) For solving this OutOfMemoryError: reason stack_trace_with_native_method is detected?
For solving use tools like >
  • pmap and
  • pstack


For more tools for various OS, please check Native Operating System Tools.


11.1) When does OutOfMemoryError : kill process or sacrifice child occurs?
OutOfMemoryError : kill process or sacrifice occurs when one of the process consumes too much virtual memory and makes OS unstable, than OS decides to kills that process.
11.2) Solution to OutOfMemoryError : kill process or sacrifice >
Increasing swap space can solve this OutOfMemoryError.
12) Exception in thread threadName : java.lang.OutOfMemoryError: permgen
12.1) When you are facing OutOfMemoryError: permgen you need to change permgen size in tomcat server?
Generally when we are facing java.lang.OutOfMemoryError - Java permgen space, then we need to change permgen size of tomcat or eclipse or JVM wherever you are facing this error.
12.2) How to set or change permgen size in tomcat server?
For setting permgen size in tomcat server you need to make changes values in the Tomcat Catalina start file. Change CATALINA_OPTS option in the file.
12.3) Where is exactly catalina.bat file located?
tomcatServerHome\bin\catalina.bat
12.4) How to set permgen size in tomcat server in windows, linux and Mac platform >
12.4.1) How to set permgen size in tomcat server in windows platform >
Open or create setenv.bat file (Location of setenv.bat file is tomcatHome\bin\setenv.bat)
set CATALINA_OPTS=-server -Xms512m -Xmx1024m -XX:PermSize=512m -XX:MaxPermSize=1024m
Best practices while setting permgen size in tomcat server in windows platform >
You should not modify tomcatServerHome\bin\catalina.bat. You should create a new file in tomcatServerHome\bin\setenv.bat to keep your custom environment configurations separate from default tomcat server configurations.


12.4.2) How to set permgen size in tomcat server in Linux platform >
Open or create setenv.sh file (Location of setenv.bat file is tomcatHome\bin\setenv.sh)
export CATALINA_OPTS="$CATALINA_OPTS=-server -Xms512m -Xmx1024m -XX:PermSize=512m -XX:MaxPermSize=1024m
Best practices while setting permgen size in tomcat server in linux platform >
You should not modify tomcatServerHome\bin\catalina.sh. You should create a new file in tomcatServerHome\bin\setenv.sh to keep your custom environment configurations separate from default tomcat server configurations.
12.4.3) How to set permgen size in tomcat server in Mac OS platform >
Open or create setenv.sh file (Location of setenv.bat file is tomcatHome\bin\setenv.sh)
export CATALINA_OPTS="$CATALINA_OPTS=-server -Xms512m -Xmx1024m -XX:PermSize=512m -XX:MaxPermSize=1024m"
Best practices while setting permgen size in tomcat server in Mac OS platform >
You should not modify tomcatServerHome\bin\catalina.sh. You should create a new file in tomcatServerHome\bin\setenv.sh to keep your custom environment configurations separate from default tomcat server configurations.
12.5) You may use following VM (JVM) PARAMETERS to set up permgen memory (or permanent generation or permanent space) >
Learn how to pass vmargs (VM parameters) to java program in eclipse?


-XX:PermSize: It’s is initial value of Permanent Space which is allocated at startup of JVM.
Example1 of using -XX:PermSize VM (JVM) option in java >
java -XX:PermSize=1g MyJavaProgram
It will set initial value of Permanent Space as 512 gigabyte to JVM
-XX:MaxPermSize: It’s maximum value of Permanent Space that JVM can allot up to.
Examples of using -XX:MaxPermSize VM option in java >
java -XX:MaxPermSize=512m MyJavaProgram
It will set maximum value of Permanent Space as 512 megabytes to JVM

For more explanation and example - Read : What are -XX:PermSize and -XX:MaxPermSize with Differences
What is the maximum perm gen size value you can set on your system, if you aren’t sure about the system configurations?
Try out for -XX:MaxPermSize=256m, if it works then try -XX:MaxPermSize=512m, if it works then try -XX:MaxPermSize=1024m and so on. Be cautious before going beyond 8g.
For more details, please read :

> OutOfMemoryError: Permgen space - How to set or change permgen size in tomcat server, eclipse?

>How to pass VM argument to tomcat in eclipse

>What are -XX:PermSize and -XX:MaxPermSize JVM parameters with examples in java | Differences
5) Summary -
So in this tutorial we learned about different OutOfMemoryError in java and how to solve them with example and programs.
Having any doubt? or you liked the tutorial! Please comment in below section.
Please express your love by liking JavaMadeSoEasy.com (JMSE) on facebook, following on google+ or Twitter.
RELATED LINKS>






Important VM parameters >

>What are -Xms and -Xmx JVM parameters in java, And differences between them with examples

>-Xmn JVM parameters in java with examples - Setting young generation size

>What are -XX:NewSize and -XX:MaxNewSize JVM parameters in java

>What are -XX:PermSize and -XX:MaxPermSize JVM parameters with examples in java | Differences

>Solve java.lang.OutOfMemoryError : unable to create new native Thread - Xss JVM option

More VM parameters >

>How to use -verbose:gc VM argument

>-Xverify option in java

Apache tomcat server,outOfMemory and Garbage collection in java >

>How to set or change permgen size in tomcat server, eclipse?

>How to set, change, increase or decrease heap size in tomcat server and eclipse to avoid OutOfMemoryError ?

>How to pass VM argument to tomcat in eclipse

Pass VM para through CMD, eclipse to java program and to Apache tomcat >

>How to write java program to pass VM/JVM parameters through CMD

>How to pass vmArgs(JVM parameters) to java program in eclipse

>How to pass VM argument to tomcat in eclipse



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