Get Garbage Collector Details

Hi,
I'm using ALBPM 6.0.4 standalone on a windows 2003.
I'm tunning the application, but when i trying to get the garbage collector details i don't get the log file.
i already set this arguments -Xloggc:../log/engine-max-gc.log -XX:+PrintGCDetails on Additional java arguments used in startup on execution tab.
I'm not sure if the engine takes this arguments on start up.
i'm doing something wrong?
Thanks in advance,
Helios.

See the javadocs for DatabaseMetaData class under java.sql

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How to get the garbage collector to work?

Hi,
i have i program where i load an image scale it down and save the scaled version in an array. I do this for a whole directory of images.
After every image i set the temporary variable for the loaded image = null and call the function System.gc().
My problem is, that the garbage collector does�nt give the memory of the loaded image free and the used memory of my program grows with every loaded image.
/* Reads all images from a folder an stores them in an Array of images */
     public static BufferedImage[] readScaledImagesFromFolder(String folder,
               int maxSize) {
          File dir = new File(folder);     /* Open the Folder */
          String[] children = dir.list();          /* Get the children of the folder */
          if (children == null) {
             // Either dir does not exist or is not a directory
              System.out.println("No images in the folder!");
              return null;
         } else {
              /* Init array for images */
              BufferedImage[] images = new BufferedImage[children.length];
              int i = 0;
              int index = 0;
              BufferedImage temp;
              String filename, fileending;
             for (i=0; i<children.length; i++) {
                  // Get filename of file or directory
                 filename = children;
     /* Get the fileending of the file */
     fileending = filename.toLowerCase().substring(filename.length()-4);
     if(fileending.equals(".jpg") || fileending.equals(".bmp")
               || fileending.equals(".png") || fileending.equals(".gif"))
          /* Read the image */
          temp = util.ImageUtils.loadBufferedImage(folder+"/"+filename);
          /* Scale the image down and save it in an array */
          images[index] = Util.getScaledImage(temp,maxSize);
          index++;
     temp = null;
     System.gc();
     Mosaic.sourceImageNum = index;
     System.out.println((index+1)+" resized pictures loaded from folder: "+folder);
     return images;
How can i get the gargabe collector to work after every iteration?
I tried to let the Thread.sleep(10) after System.gc() but it does�nt help.
Thank you every much
JackNeil

Hm yes.. i now that System.gc() is only a
suggestion.
But i know what my program is doing and that it
does�nt need the temporary image anymore after i have
a scaled down version. And the temporay image will become unreachable as soon as reading the next one overwrites your temp variable. Setting the variable to null doesn't have much effect.
It would be smarter to load the new image over the
old temporary image and not to expand the heapsize to
maximum.Then look at the possibitly of loading the next image into the same bufferedimage.

Annotations & Garbage collector study matirials. Where I can get it?

Where I can get it good tutorials about annotations & Garbage collector ?
thank you

Did you try Google?
http://www.google.com/search?q=java+annotations+tutorial
http://www.google.com/search?q=java+garbage+collection+tutorial

How the protected finalize method is called by garbage collector

Dear All,
I have a double regarding the calling mechanism of finalize method. The access specifier of finalize method is protected, not only that if a class overrides this method then also the finalize method can be protected in the subclass of Object. But the concept of protected access specifier is, from outside of the package it can be accessed only from subclass.
The program (may be part of Garbage collector), which calls this (finalize) method mast not be in the same package (that is java.jang) nor it is a subclass of the class (whose finalize method it calls).
Then how the finalize method is getting called by the garbage collector when it is protected?
Regards,
Gourab

Refer to following link for the details
http://www.me.umn.edu/~shivane/blogs/cafefeed/2005/09/why-is-finalize-method-protected.html
The link gives answer to how a protected/private members are accessible to JVM or GC and why finalize is declared protected.

Garbage Collector Agent

Hello, I want to know if the Garbage Collector deletes UnFoldered Document. I have created a custom relationship (ThumbnailRelationship) to attache a thumbnail file (a jpeg) to documents. Now, when some one delete a Document, do I have to create a Override to manually delete the ThumbnailRelationship and the Thumbnail document or the Garbage Collector will take care of it ? Where can I get more info on all those Agents running in the background ?
Thank you
null

Hi -
No, the GarbageCollectionAgent does not delete unfoldered objects. It cleans up references to objects that have been deleted. For example, say a user names testuser1 owns several documents. Then this user gets deleted - who owns the documents? Or more specifcally, what is the value stored in the owner column in the database table? The GarbageCollectionAgent firsts nulls these attributes, and for some attributes (PublicObject.Owner being one of them) it resets the existing objects to reference some other object.
So, if you want the rightobject of a custom relationship to be automatically deleted when the leftobject is deleted, you'll have to do that via an override on your custom relationship subclass.
I think the new admin guide has some more detailed information about the out-of-the-box agents.
hope this helps-
dave

Garbage collector in java

Hi all,
How does a garbage collector knows, when it should deallocate the memory of an
object ?. And How can we make ready an object to deallocate it's memory by garbage collector ?.

Hi all, Hi!
How does a garbage collector knows, when it
should deallocate the memory of an
object ?.Objects are kept in a memory heap, and the objects that are having references are called dirty objects, and objects with no references are called clean objects(I think so, don't believe me).
clean objects (and objects with weak references) are liable for garbage collection.
there are certain thresold conditions (which I don't know), when they are reached, gc runs.
These thresold conditions are jvm specific(jvm optimization), one could be when jvm feels it is going to get out of memory(again, don't believe me). You would have to go into details of jvm for that(I don't want to go there as I have lots of other things to learn).
And How can we make ready an object
to deallocate it's memory by garbage collector ?.there is no way you can control gc mechanism manually, because jvm have to take care of a lots of optimizations. so you can't predict when your object will be collected by gc.
(that's why people don't beleave on finalize method).

Incremental Garbage Collector is halting my server for MINUTES at a time.

I have a Java server which services hundreds (currently 300-700 on average, target of 2000+) of simultaneous client connections, with a staggering number of long lived (but not permanent) objects.
The docs for incremental garbage collection state: "The incremental garbage collector, which is off by default, will eliminate occasional garbage-collection pauses during program execution." This is NOT true in my case. During peak load, the Server halts occasionally (once an hour or more) and entire MINUTES tick by. Average wait time is 2.5 - 3.5 minutes, the highest I have seen is 4 minutes, 10 seconds. This is entirely unnacceptable.
The server is on Red Hat Linux 6.2, kernel 2.2.14-5.0, with a gig of RAM. My current command line options are
java -server -Xincgc -Xms256M -Xmx900M
And I have just added -verbose:gc to help analyze the gc performance. I have read the gc tuning guide at http://java.sun.com/docs/hotspot/gc/index.html but still feel rather clueless about what is the optimum setup for my particular application.
I will of course start experimenting, but I was hoping to find a "wise old elf" who might give some useful pointers to accelerate the process, seeing as how the Server is already running in a production capacity, time is critical.

Are you using a Java application server like Tomcat, Dynamo, WebLogic etc. ?
In that case consider running several server instances on the machine, with the applicationserver's software load balancer. Find the amount of RAM allocated to the heap per serverinstance where garbage collection runs takes a couple of seconds, and don't allocate more than this to each server. Start as many servers as you have available RAM for.
This is the approach recommended by application server vendors such as BEA http://edocs.bea.com/wls/docs61/perform/JVMTuning.html and ATG.
A side benefit of this approach is that in case you get more concurrent users than your computer can handle, you already have the setup for spreading the load over several computers.

Garbage collector don't works.

Hello people !
When I restart the weblogic server this do not shows the lastest change that I made. I think the problem is related to the garbage collector and its bean tree.
Do you known how to solve this?
Thank you.
Regards.

I'm working with WebLogic Server 10.0 and the problem is if I restart the server this don't holds the lastest change that I made, it happens with any type of change (deploy, undeploy, create or delete servers/services, etc).
I've reviewed the log file and I've found the following error:
<Jun 2, 2008 6:45:14 PM CDT> <Warning> <Management> <BEA-141269> <The temporary bean tree updateDeploymentContext(Mon Jun 02 10:46:11 CDT 2008) was allocated for an undo, get, or activate operation, but has not been garbage collected.>
Stopping PointBase server...
PointBase server stopped.
Thank you for your attention

EMCC and Garbage Collector

We have 2 CUCM clusters connected via an ICT. We are migrating users from CM8.6 to CM10.5. During the migration we are changing Users AD attributes so that they disappear from CM8. As this marks the user as Inactive in CM8 (and deletes after 24hrs) this prevents the User from logging into CM10 with EMCC.
Is there a way around this?
ie force the garbage collector to run immediately and delete the user
or remove certain fields in CUCM 8 against the user so that they can login using CUCM10 credentials?
Thanks
Rich

I think you can do something clever here. You can convert the inactive user on cucm 8 back to a standard cucm user and then delete them. This way you can control when to remove the user instea dof waiting for garbage collection. You become your own garbage man :)
You can conver the users back to standard CUCM users using sql query update...Ths is easy to do
run sql update enduser set status=1 ( this is the general command to make all users standard cucm users..you don't want to run this..)
Use this command to make specific users active. You need to use the users extension to filter which user gets converted to standard cucm user
run sql update enduser set status=1 where telephonenumber like ‘2%’
This command will update users with extension beginning with 2
or
run sql update enduser set status=1 where telephonenumber = '2001'
This will convert user with extension 2001 to a standard cucm user
To make sure you got all the users you can use the command
run sql select * from enduser where status=0
This should return zero entry. If you find any user there then use the update command on those users

I have a memory leak, objective-c 2.0, and garbage collector...

the code i am using is a modification of the code/problem found in "Cocoa with Objective-C", chapter 3.
i have tried to use the objective-c 2.0 garbage collector methodology, using @property, @synthesize, etc. when i run the code as listed below i get a leaking message.
[Session started at 2008-02-01 23:33:37 -0500.]
2008-02-01 23:33:38.070 SongsFoundationTool[28876:10b] * _NSAutoreleaseNoPool(): Object 0x2040 of class NSCFString autoreleased with no pool in place - just leaking
Stack: (0x96b10178 0x96a3e0f8)
2008-02-01 23:33:38.075 SongsFoundationTool[28876:10b] Song 1: We Have Exposive
2008-02-01 23:33:38.076 SongsFoundationTool[28876:10b] * _NSAutoreleaseNoPool(): Object 0x2060 of class NSCFString autoreleased with no pool in place - just leaking
Stack: (0x96b10178 0x96a3e0f8)
2008-02-01 23:33:38.078 SongsFoundationTool[28876:10b] Song 2: Loops of Fury
The Debugger has exited with status 0.
when i include the commented out section, in the implementation file section, the description method, and use song1 and song2, in main, instead of song1.name and song2.name the program seems to run fine.
The Debugger has exited with status 0.
[Session started at 2008-02-01 23:38:24 -0500.]
2008-02-01 23:38:24.375 SongsFoundationTool[28936:10b] Song 1: We Have Exposive
2008-02-01 23:38:24.379 SongsFoundationTool[28936:10b] Song 2: Loops of Fury
The Debugger has exited with status 0.
please help me understand what's happening here.
also, why was it necessary to use
@property(copy, readwrite) NSString *name;
@property(copy, readwrite) NSString *artist;
instead of
@property(readwrite) NSString *name;
@property(readwrite) NSString *artist;
thanks everyone, the code is below.
// ....................... header file ...............
#import <Cocoa/Cocoa.h>
@interface Song : NSObject {
NSString *name;
NSString *artist;
@property(copy, readwrite) NSString *name;
@property(copy, readwrite) NSString *artist;
@end
//.................... the implementation file ..................
#import "Song.h"
@implementation Song
@synthesize name;
@synthesize artist;
-(NSString *) description
return [ self name ];
@end
//................................ main............................
#import <Foundation/Foundation.h>
#import "Song.h"
int main (int argc, const char * argv[]) {
Song *song1 = [ [ Song alloc ] init ];
song1.name= @"We Have Exposive" ;
[ song1 setArtist: @"The Future Sound Of Londown" ];
Song *song2 = [ [ Song alloc ] init ];
[ song2 setName: @"Loops of Fury" ];
[ song2 setArtist: @"The Chemical Brothers" ];
// Display Object
NSLog( @"Song 1: %@", song1.name );
NSLog( @"Song 2: %@", song2.name );
// include statements below if -description method is uncommented
// then comment out the two statements above. no memory leak if the code
// is used from the statements below and - description is not commented out and
// the two NSLog statements above are commented out.
NSLog( @"Song 1: %@", song1 );
NSLog( @"Song 2: %@", song2 );
return 0;
}

Normally, your main only has a call to NSApplicationMain(). If you aren't doing a traditional MacOS X application, you will still want at least NSApplicationLoad() to get enough of the runtime to avoid those messages.
I don't know for sure about the syntax of Objective-C 2.0. That stuff is all new. What error message are you getting that indicated that (copy, readwrite) is required? Could you provide a link to the actual example source? I did a quick check and assign and readwrite are the defaults. It is possible that readwrite by itself makes no sense. But I'm just guessing.

How intelligent is the garbage collector?

Hi all,
I've got a question about how garbage collection works in an ABAP objects context.
If there are no more references an object is cleaned up and the memory released. Fine.
What about an object O1, which in turn creates another object O2. O2 however also contains a refernce to O1.
When the original process completes, this leaves two objects that reference each other, but with no other contact to the 'outside world'. Is the garbage collector intelligent enough to dump them?
Any input appreciated,
Cheers
Mike

Hi,
Thanks for the feedback. I am still not sure - you say 'when the program ends it's part'. This is exactly the point - when the program ends, do the objects remain because they still contain references to each other?
More detail:
The references are public instance attributes of both objects (different classes). I would prefer to use functional methods, but am stuck with public attributes which I'm populating in the constructor.
So a process P declares a local var LV_O1 and does a CREATE OBJECT LV_O1.
In the constructor of O1, it does a
CREATE OBJECT me->ATTR_O2 to populate it's attribute with a reference to an instance of O2.
O2 doesn't need to do a CREATE OBJECT, but assigns a ref to O1 to it's attribute ATTR_O1.
So now O1 and O2 refer to each other by public attributes:
O1->ATTR_O2 and O2->ATTR_O1.
The big question is what happens when process P ends and it's variable LV_O1 ceases to exist?
In case anyone's wondering about the overall wisdom of the design, they have to be public attributes (used in Workflow) and they have to refer to each other as instantiation may also happen the other way around.
Cheers
Mike

About Garbage Collector

In Java, there is one system call for garbage collector.
System.gc();
I want to know the significance of this system call for GC. Even after calling this method, garbage collector won't get started, still it will run on its own time.
If this is the thing then what's the significance of this method call?
Please let me know this.
Thanking you,
Ketan

Addendum
In a heavy data application, for instance, that stores records in memory for some purpose, then releases that memory and creates next set of records in memory, calling gc really help.
We have such application where in we tested its performance with and without calling gc. No wonder, we found better results by calling gc.

Automatic Garbage collector after JVM almost hit max value on weblogic ?

Hi All,
I have application on weblogic 10MP2. I use 4G JVM. My application getting slow when the usage of JVM hit arround 70-80% of max heap size. Unfortunatelly, the garbage collector didn't run when it hit that high. So to keep my application in good state, I need to MANUALLY hit the Perform GC to keep the JVM below 70%.
Is there any settings to tell the JVM to perform GC when the free space of the JVM hit 30%?
What will the weblogic do if one of the server in warning state? There is a settings in the weblogic to specify when it hit some percentage of free space, it will bring the server to warning state. Will it do the Garbage Collector?
Need your help on this. I am tired of hitting the Perform GC button.
Really appeciate your help.
Thanks,
Eric

I am replying to my own post because I found a tool that
helped me solve in two hours what I had been stumped on
for the past few days.
The Heap Analysis Tool.
I had a major memory leak problem. I couldn't locate
the source until I downloaded and used this tool(for free).
This tool keeps track of memory used by objects,
each objects references, objects references by each
object, and all objects instances. All of this information
can be obtained in html format for efficient traversing
of object chains. I would highly recommend looking
this tool over if you intend on doing memory intensive
programming.
In case your curious where my error was I had two problems
which are now fixed. One. I had a couple of BufferedImages
that were leaking 30MB RAM. Two. I didn't know that using
ObjectStream's to read/write objects stored references
to the objects being written(preventing garbage collection).
Deffinately worth running the Heap Analysis Tool before
pointing a finger at System.gc().

Error "The current garbage collector has no nursery"

Has anybody any information on the error message "The current garbage collector has no nursery"? We received the following error message after starting the WLS in production mode:
<2006-jan-25 kl 17:57 CET> <Error> <Management> <BEA-140001> <An error occurred while getting attribute TotalNurserySize on MBean se-i-ld09:Location=se-i-ld09-c01-s01,Name=se-i-ld09-c01-s01,ServerRuntime=se-i-ld09-c01-s01,Type=JRockitRuntime. Method: public long weblogic.t3.srvr.JRockitRuntime.getTotalNurserySize(). Exception: com.bea.jvm.NotAvailableException: The current garbage collector has no nursery..
com.bea.jvm.NotAvailableException: The current garbage collector has no nursery.
     at jrockit.management.jvm.GarbageCollectorImpl.getNurserySize()J(Unknown Source)
     at weblogic.t3.srvr.JRockitRuntime.getTotalNurserySize()J(JRockitRuntime.java:112)
     at jrockit.reflect.NativeMethodInvoker.invoke0(Ljava.lang.Object;ILjava.lang.Object;[Ljava.lang.Object&amp)Ljava.lang.Object;(Unknown Source)
     at jrockit.reflect.NativeMethodInvoker.invoke(Ljava.lang.Object;[Ljava.lang.Object&amp)Ljava.lang.Object;(Optimized Method)
     at jrockit.reflect.VirtualNativeMethodInvoker.invoke(Ljava.lang.Object;[Ljava.lang.Object&amp)Ljava.lang.Object;(Optimized Method)
     at java.lang.reflect.Method.invoke(Ljava.lang.Object;[Ljava.lang.Object;I)Ljava.lang.Object;(Optimized Method)
     at weblogic.management.internal.DynamicMBeanImpl.getAttribute(Ljava.lang.String&amp)Ljava.lang.Object;(DynamicMBeanImpl.java:574)
     at com.sun.management.jmx.MBeanServerImpl.getAttribute(Ljava.lang.Object;Ljava.lang.String&amp)Ljava.lang.Object;(MBeanServerImpl.java:1183)
     at com.sun.management.jmx.MBeanServerImpl.getAttribute(Ljavax.management.ObjectName;Ljava.lang.String&amp)Ljava.lang.Object;(MBeanServerImpl.java:1153)
     at weblogic.management.internal.RemoteMBeanServerImpl.getAttribute(Ljavax.management.ObjectName;Ljava.lang.String&amp)Ljava.lang.Object;(RemoteMBeanServerImpl.java:287)
     at weblogic.management.internal.RemoteMBeanServerImpl_WLSkel.invoke(ILweblogic.rmi.spi.InboundRequest;Lweblogic.rmi.spi.OutboundResponse;Ljava.lang.Object&amp)Lweblogic.rmi.spi.OutboundResponse;(Unknown Source)
     at weblogic.rmi.internal.BasicServerRef.invoke(Lweblogic.rmi.extensions.server.RuntimeMethodDescriptor;Lweblogic.rmi.spi.InboundRequest;Lweblogic.rmi.spi.OutboundResponse&amp)V(BasicServerRef.java:477)
     at weblogic.rmi.internal.BasicServerRef$1.run()Ljava.lang.Object;(BasicServerRef.java:420)
     at weblogic.security.acl.internal.AuthenticatedSubject.doAs(Lweblogic.security.subject.AbstractSubject;Ljava.security.PrivilegedExceptionAction&amp)Ljava.lang.Object;(AuthenticatedSubject.java:363)
     at weblogic.security.service.SecurityManager.runAs(Lweblogic.security.acl.internal.AuthenticatedSubject;Lweblogic.security.acl.internal.AuthenticatedSubject;Ljava.security.PrivilegedExceptionAction&amp)Ljava.lang.Object;(SecurityManager.java:144)
     at weblogic.rmi.internal.BasicServerRef.handleRequest(Lweblogic.rmi.spi.InboundRequest&amp)V(BasicServerRef.java:415)
     at weblogic.rmi.internal.BasicExecuteRequest.execute(Lweblogic.kernel.ExecuteThread&amp)V(BasicExecuteRequest.java:30)
     at weblogic.kernel.ExecuteThread.execute(Lweblogic.kernel.ExecuteRequest&amp)V(ExecuteThread.java:219)
     at weblogic.kernel.ExecuteThread.run()V(ExecuteThread.java:178)
     at java.lang.Thread.startThreadFromVM(Ljava.lang.Thread&amp)V(Unknown Source)>
Thanks in advance for your help - it is much appreciated!
    Cheers, Jonas

This exception is thrown by the JRockit Management API when querying the nursery size of a GC that has no nursery (single-generational GC). The logical place to catch the error would be in the weblogic.t3.srvr.JRockitRuntime.getTotalNurserySize() method, which implies that it is a WLS issue.
Maybe it has been fixed in a later WLS 8.1 service pack?
If you run with a generational GC, i.e. "-Xgc:gencon" the error will go away, but that has larger implications on the behavior of your app so it should not be used as a workaround.

Problem with garbage collector -

I'm experiencing a problem with the Java Garbage Collector.
It simply doesn't work when I try to free the memory that is used
by an object in my program...
I explicitly declared this object as null, and called System.gc, but it seems it isn't working.
What might be the reason?
This object uses a lot of memory. Therefore, I MUST destroy it after it's no longer
needed.

Ok. I'll try to be more specific...
My "situation" seems something like that
class Program {
Xclass class1;
void method1() {
class1 = new Xclass();
} (End of class Program)
class Xclass {
Yclass class2;
Public Xclass( ) {
class2 = new Yclass();
add(class2);
} (end of class Xclass)
class Yclass {
Public Yclass(Container parent) {
(no explicit reference to Xclass or Program classes or any variable or instantiations of said classes);
} (end of class Yclass)
Well, I know that the gc is not being done because the first time I call method1 everything goes fine. But When I try it again an OutOfMemoryError happens...
I tried to do the following (I know, it's not elegant, but I just wanted to get some results):
void method1() {
class1 = null;
System.gc();
class1 = new Xclass();
Again it worked in the first time. But later...

Get Garbage Collector Details

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