Concurrent access

Hi all,
I have created a BAPI which is working well.
However, if I call it more than one times at the same times through RFC (php call), it doesn't work correctly.
Can anyone help me about concurrent access like this ?
Thanks,
Smoltok

Hello,
Before the call to your BAPI, call the function module ENQUEUE_<name of the lock object> and pass the parameters to locjk the specific entry. Now all your BAPI amd once done unlock the entry by call the function module DEQUEUE_<name of the lock object>.
Regards,
Sachin

Similar Messages

How to synchronize concurrent access to static data in ABAP Objects

Hi,
1) First of all I mwould like to know the scope of static (class-data) data of an ABAP Objects Class: If changing a static data variable is that change visible to all concurrent processes in the same Application Server?
2) If that is the case. How can concurrent access to such data (that can be shared between many processes) be controlled. In C one could use semaphores and in Java Synchronized methods and the monitor concept. But what controls are available in ABAP for controlling concurrent access to in-memory data?
Many thanks for your help!
Regards,
Christian

Hello Christian
Here is an example that shows that the static attributes of a class are not shared between two reports that are linked via SUBMIT statement.
*& Report ZUS_SDN_OO_STATIC_ATTRIBUTES
REPORT zus_sdn_oo_static_attributes.
DATA:
gt_list TYPE STANDARD TABLE OF abaplist,
go_static TYPE REF TO zcl_sdn_static_attributes.
* CONSTRUCTOR method of class ZCL_SDN_STATIC_ATTRIBUTES:
**METHOD constructor.
*** define local data
** DATA:
** ld_msg TYPE bapi_msg.
** ADD id_count TO md_count.
**ENDMETHOD.
* Static public attribute MD_COUNT (type i), initial value = 1
PARAMETERS:
p_called(1) TYPE c DEFAULT ' ' NO-DISPLAY.
START-OF-SELECTION.
* Initial state of static attribute:
* zcl_sdn_static_attributes=>md_count = 0
syst-index = 0.
WRITE: / syst-index, '. object: static counter=',
 zcl_sdn_static_attributes=>md_count.
DO 5 TIMES.
* Every time sy-index is added to md_count
 CREATE OBJECT go_static
 EXPORTING
 id_count = syst-index.
 WRITE: / syst-index, '. object: static counter=',
 zcl_sdn_static_attributes=>md_count.
* After the 3rd round we start the report again (via SUBMIT)
* and return the result via list memory.
* If the value of the static attribute is not reset we would
* start with initial value of md_count = 7 (1+1+2+3).
 IF ( p_called = ' ' AND
 syst-index = 3 ).
 SUBMIT zus_sdn_oo_static_attributes EXPORTING LIST TO MEMORY
 WITH p_called = 'X'
 AND RETURN.
 CALL FUNCTION 'LIST_FROM_MEMORY'
 TABLES
 listobject = gt_list
 EXCEPTIONS
 not_found = 1
 OTHERS = 2.
 IF sy-subrc <> 0.
* MESSAGE ID SY-MSGID TYPE SY-MSGTY NUMBER SY-MSGNO
* WITH SY-MSGV1 SY-MSGV2 SY-MSGV3 SY-MSGV4.
 ENDIF.
 CALL FUNCTION 'DISPLAY_LIST'
* EXPORTING
* FULLSCREEN =
* CALLER_HANDLES_EVENTS =
* STARTING_X = 10
* STARTING_Y = 10
* ENDING_X = 60
* ENDING_Y = 20
* IMPORTING
* USER_COMMAND =
 TABLES
 listobject = gt_list
 EXCEPTIONS
 empty_list = 1
 OTHERS = 2.
 IF sy-subrc <> 0.
* MESSAGE ID SY-MSGID TYPE SY-MSGTY NUMBER SY-MSGNO
* WITH SY-MSGV1 SY-MSGV2 SY-MSGV3 SY-MSGV4.
 ENDIF.
 ENDIF.
ENDDO.
* Result: in the 2nd run of the report (via SUBMIT) we get
* the same values for the static counter.
END-OF-SELECTION.
Regards
Uwe

Concurrent access in Diadem

How does Dia dem manages concurrent access?
If several network users each of them having a floating licence, want to access the same objects (datasets, reports, view layout), can they?
What happens if they want to load/delete/modify datasets located in the same folder?
And if they want to write on the same report?
Thanks

Hi condor31,
The only thing which is concurrent is the license file. The DIAdem installation is still local on the client computer, which means that client A's DIAdem is completely separate from client B's DIAdem, because the two DIAdems are running on completely different computers. So you don't have to worry about collisions at the REPORT object level at all. If DIAdem A and DIAdem B attempt to access or update the same external files (layout files, data files, etc.), then the usual file access rules apply. Both DIAdem A and DIAdem B can load the same layout or data file from computer C, say, and play with them back on computers A and B, respectively. If DIAdem A then overwrites the layout or data file on computer C with an updated version, DIAdem B doesn't notice, because DIAdem B has those files in memory on computer B. If DIAdem B subsequently overwrites the layout or data file on computer C, then DIAdem B wins and its version of the file is now on computer C, though DIAdem A doesn't know this has happened. If you want to protect a particular data or layout file, you can of course set its Windows read-write permissions to read-only, then neither DIAdem A nor DIAdem B will be able to change it, though they will be able to read it and use it and save the edited version to a new data or layout file.
The one exception to this is if DIAdem A and DIAdem B happen to register-load the same data file, then they each have an implicit link back to the data file on computer C, and neither will be able to change that data file, since register-loading opens the data file read-only and puts a lock on it so that no one can change it while you have it open, but this is a special case.
Brad Turpin
DIAdem Product Support Engineer
National Instruments

How does the Concurrent Access License (CAL) work.

Description from Google: How does the Concurrent Access License (CAL) work? Xcelsius Engage Server CALs allow for concurrent live data updates inside Xcelsius dashboards. Every time an end-user triggers a Web service inside an Xcelsius dashboard to retrieve live data, a CAL is consumed for a period of 5 minutes. For that period, in a five CAL deployment for example, there will be only four CALs left for consumption. A five CAL deployment could support up to 25 users and additional CALs can be added to support a larger deployment.
My question is as follows:
How a five CAL deployment could support up to 25 users and what does it mean. In the first line it is saying that each CAL for a web service is consumed for a period of 5 minutes and how come it can support 25 users concurrently. Did it mean 25 web service connections inside a swf flash file or 25 different users to access a single web service through swf flash.

The "Set cost controls" concurrent program is used in R12 to mass update the cost control fields on item costs.
The cost control region is found by going to Cost management >Item costs > Item Costs
The concurrent program lets you specify which items /costs should be updated by using various parameters such as cost type, item range, category range etc.
And you can specify the source for the new cost control data and the new value for the fields.
Hope this answers your question,
Sandeep Gandhi

Concurrent Access for Crystal Reports for eclipse

Hi,
May i know is there any concurrent access limitation when viewing the reports in web using JRC?

The performance does get better after the initialization of the JRC application. Because it is a pure java application without any reliances on servers for processing power, it will rely on the speed of the application server. In the initialization, all of the libraries get loaded in to the classpath so this does take some time. Generally speaking the performance will get better after this because everything has been loaded in to memory; that is until you restart the application server.
The JRC will be a bit slower when rendering a large report. Depending on the size of that report, you may be looking at between a few seconds and several minutes in processing time.
Whether or not you use the JRC will depend on the number of users you anticipate having at any given time for your application as well as the general size of your reports.
Crystal Reports Server comes with a set number of licenses. Initially it comes with 5 and you can purchase up to 20 or 25. This means you could potentially have about the same number of users as you would with a JRC application, but if you have large reports then you could take advantage of the benefit of being able to schedule those reports (set them to run during an off time so your users can view the instances quickly when they need to). You do have to be more mindful of how you use licenses with this product, since for each user logged on to the system there will be a license used. There are many additional benefits, including performance that can be had with CR Server. One key difference would be in the cost of the product: The JRC is essentially free, whereas CR Server is not.
I would suggest reading our product documentation and applying it to your situation to determine what implementation would work best for you.

Shared data - concurrent access

Entity beans are best used when shared data is being concurrently accessed.
Could you please clarify this statement . How does it different than shared data - concurrent access by jdbc DAO class ?

jverd wrote:
I have no idea what you're asking. I cannot provide clarification until you do.Ok. let me explain further. my question is , is it a good idea that whenever we need shared concurrent data access in a application Entity bean is the best ? Why? does it really outsmart the jdbc DAO access methodology whenever it comes to the realm of shared concurrent data access ?
For example: I can think of a system e.g online auction house application. This needs concurrent shared data access ..right ?
Do you think use of Entity bean is best here instead of jdbc DAO access methodology ? Why ?

Unexpected error occurred :concurrent access to HashMap attempted

While runnig the ALBPM 5.7 we got this error. This looks like the ALBPM workflow engine is using HashMap in a unsynchronized way. is this a known issue and is there a work around for this?
This error happened shortly after a possible blip in the database server, with exception message which said:
Message:
The connectivity to the BEA AquaLogic™ BPM Server database has been successful restablished.
Any thoughts/insight/past experience....
Looks like we should be using Hashtable instead of a HashMap (or atleast a Synchronized HashMap)
This is best done at creation time, to prevent accidental unsynchronized access to the map:
Map m = Collections.synchronizedMap(new HashMap(...));
See Exception message below
Message:
An unexpected error occurred while running an automatic item.
Details: Connector [ffmaeng_ENGINE_DB_FUEGOLABS_ARG:SQL:Oracle (ALI)] caused an exception when getting a resource of type [0].
Detail:Connector [ffmaeng_ENGINE_DB_FUEGOLABS_ARG:SQL:Oracle (ALI)] caused an exception when getting a resource of type [0].
Caused by: concurrent access to HashMap attempted by Thread[ET(49),5,Execution Thread Pool]
fuego.connector.ConnectorException: Connector [ffmaeng_ENGINE_DB_FUEGOLABS_ARG:SQL:Oracle (ALI)] caused an exception when getting a resource of type [0].
Detail:Connector [ffmaeng_ENGINE_DB_FUEGOLABS_ARG:SQL:Oracle (ALI)] caused an exception when getting a resource of type [0].
at fuego.connector.ConnectorException.exceptionOnGetResource(ConnectorException.java:95)
at fuego.connector.ConnectorTransaction.getResource(ConnectorTransaction.java:285)
at fuego.connector.JDBCHelper.getConnection(JDBCHelper.java:43)
at fuego.server.service.EngineConnectorService.getConnection(EngineConnectorService.java:260)
at fuego.server.service.EngineConnectorService.getEngineConnection(EngineConnectorService.java:160)
at fuego.transaction.TransactionAction.getEngineHandle(TransactionAction.java:180)
at fuego.server.execution.EngineExecutionContext.getEngineHandle(EngineExecutionContext.java:352)
at fuego.server.execution.EngineExecutionContext.persistInstances(EngineExecutionContext.java:1656)
at fuego.server.execution.EngineExecutionContext.persist(EngineExecutionContext.java:1010)
at fuego.transaction.TransactionAction.beforeCompletion(TransactionAction.java:133)
at fuego.connector.ConnectorTransaction.beforeCompletion(ConnectorTransaction.java:654)
at fuego.connector.ConnectorTransaction.commit(ConnectorTransaction.java:330)
at fuego.transaction.TransactionAction.commit(TransactionAction.java:303)
at fuego.transaction.TransactionAction.startBaseTransaction(TransactionAction.java:470)
at fuego.transaction.TransactionAction.startTransaction(TransactionAction.java:540)
at fuego.transaction.TransactionAction.start(TransactionAction.java:213)
at fuego.server.execution.DefaultEngineExecution.executeImmediate(DefaultEngineExecution.java:118)
at fuego.server.execution.DefaultEngineExecution.executeAutomaticWork(DefaultEngineExecution.java:58)
at fuego.server.execution.EngineExecution.executeAutomaticWork(EngineExecution.java:42)
at fuego.server.execution.ToDoItem.executeAutomaticWork(ToDoItem.java:264)
at fuego.server.execution.ToDoItem.run(ToDoItem.java:531)
at fuego.component.ExecutionThread.processMessage(ExecutionThread.java:754)
at fuego.component.ExecutionThread.processBatch(ExecutionThread.java:734)
at fuego.component.ExecutionThread.doProcessBatch(ExecutionThread.java:140)
at fuego.component.ExecutionThread.doProcessBatch(ExecutionThread.java:132)
at fuego.fengine.ToDoQueueThread$PrincipalWrapper.processBatch(ToDoQueueThread.java:432)
at fuego.component.ExecutionThread.work(ExecutionThread.java:818)
at fuego.component.ExecutionThread.run(ExecutionThread.java:397)
Caused by: java.util.ConcurrentModificationException: concurrent access to HashMap attempted by Thread[ET(49),5,Execution Thread Pool]
at java.util.HashMap.onExit(HashMap.java:226)
at java.util.HashMap.transfer(HashMap.java:690)
at java.util.HashMap.resize(HashMap.java:676)
at java.util.HashMap.addEntry(HashMap.java:1049)
at java.util.HashMap.put(HashMap.java:561)
at fuego.lang.cache.CacheStatistic.lock(CacheStatistic.java:246)
at fuego.lang.cache.TimedMultiValuatedCache.getLocked(TimedMultiValuatedCache.java:282)
at fuego.lang.cache.TimedPool.get(TimedPool.java:80)
at fuego.connector.impl.BaseJDBCPooledConnector.getConnection(BaseJDBCPooledConnector.java:140)
at fuego.connector.impl.BaseJDBCConnector.getResource(BaseJDBCConnector.java:222)
at fuego.connector.ConnectorTransaction.getResource(ConnectorTransaction.java:280)
... 26 more

Hi BalusC,
I forgot to tell one thing, the exception what I mentioned is coming very rarely. The application is in Production and they getting this Exception once in 3 months. Is there any way to re-produce the same exception number of times to check whether it has been fixed or not after installing the updates as you said. If you have any information regarding this exception please send me.
Thank You.

What is CR returned error code / status when hit max concurrent access ?

Hi,
Do anyone knows what is the returned error code or status return from crystal report object when it hits its max concurrent access license?
I'm developing on VS 2005 With crystal report, which comes along with it. If i'm not wrong its CR 9. Correct me if I got e versioning wrong. =)
Thanks in advance!!

Hi,
Do anyone knows what is the returned error code or status return from crystal report object when it hits its max concurrent access license?
I'm developing on VS 2005 With crystal report, which comes along with it. If i'm not wrong its CR 9. Correct me if I got e versioning wrong. =)
Thanks in advance!!

Segment fault in concurrent access to BDB

Hi, All
I am extending a single thread BDB application to allow concurrent
access to the DB from 2 threads, transaction is not needed.
The environment is opened with the flag (DB_CREATE | DB_INIT_MPOOL | DB_INIT_LOCK).
Then I open a new DB under the same directory in each thread, and
modify the DB simultaneously. my expectation was that each thread
will not conflict with each other and in turn improve the
throughput. While the program constantly crashed because of segment
fault in file (src/lock/lock.c:832, both threads crashed on this
line).
I inspected the back trace, the only suspecious thing I found is that
the 2 threads are using the same locker object[1], so I'm wondering if
anyone has similar experience implementing concurrent BDB
applications? And what's possible cause of my problem and possible
fixes? Thanks.
[1]
thread 1: #0 0x00002aaab3651a7f in __lock_get_internal (lt=0x13cbda0, sh_locker=0x2aab0119f258, flags=4, obj=0x1c55650, lock_mode=DB_LOCK_WRITE, timeout=0, lock=0x2aab449fe8a0)
at ../src/lock/lock.c:832
thread 2: #0 0x00002aaab3651a7f in __lock_get_internal (lt=0x13cbda0, sh_locker=0x2aab0119f258, flags=4, obj=0x13da640, lock_mode=DB_LOCK_WRITE, timeout=0, lock=0x2aab3ffc78a0)
at ../src/lock/lock.c:832

Hi, Mike
Thanks for the timely reply!
I referred to the Berkeley DB Transaction Guide, while the doc does not mention the consequence if you violate the scenario requirement.
1. I choose the default Data Store model, and my program will allow multiple writers, what's the expected behavior? 2 threads using the same locker compete different locks is supposed to segment fault? I'm also curious about how a put(key, data) correspond to a locker, keys in the memory page map to the same locker?
2. I try to enable concurrent reader & writer without transaction, while the guide assumes transaction is enable, is Data Store able to achieve this? Or at least Concurrent Data Store is required?
Thank you very much!

Concurrent access to a SortedMap

i need a Map data structure which would allow concurrent access (like ConcurrentHashMap) while being able to return elements in a defined order (like SortedMap) for my application. i'm using Java SE 5.
how do i create this sort of data structure?
can SortedMaps be somehow wrapped with ConcurrentHashMap similar to:
Collections.synchronizedMap(new TreeMap());
?

can SortedMaps be somehow wrapped with
ConcurrentHashMap similar to:
Collections.synchronizedMap(new TreeMap());
Sure, you could do that. Although the synchronized map view returned by Collections.synchronizedMap offers only the Map interface (not SortedMap), you'll still have the guarantee that the key/value pairs are sorted by their keys, thus you'll be able to iterate in a defined order, as you requested. Anyway, there is also Collections.synchronizedSortedMap!
OTOH, the keyword "iteration" already points to a caveat:
iterating a map is usually done by iterating either its entrySet or its keySet (with subsequent value-retrieval). Even when using a synchronized map view, access to the entry set or key set will need to be synchronized manually as described in the JavaDocs.
Generally speaking, the Collections.synchronized... views are rarely useful at all, since code blocks that need to be executed atomically almost always include more than one access to the collection.

Concurrent Access Licenses

Post Author: pkumar
CA Forum: Authentication
I am getting the following error while trying to logon into CMC:
All of your system's 0 Concurrent Access Licenses are in use at this time or your system's license key has expired. Try again later or contact your administrator to obtain additional licenses.
I have 10 named user licenses for 180 days trial version.
Using a
1.> System DSN with Windows NT authentication
2.> CMS server IP address
3.> CMS server port number :6400
While installing if I use a File DSN it does not allow me to move to the next step of Installable.
Thank You
PKumar

Post Author: kconner
CA Forum: Authentication
Pkumar,
Not sure if this answers your question but I would probably set up for your 10 users, set up a "generic" Crystal Enterprise user Name /PW combo rather than trying to Authenticate via LDAP/Active Directory; soemthing like company abbrev1 (no spaces) , pw1. See if that works, then move on to more complicated LDAP authen

Flex and concurrent access

I am going to work on a new project. This project is a real time scanning processing monitor. The application would launch from an html wrapper. Also a few more processes will also start from there using JavaScript code:
oReadfromScanner1 = new ActiveXObject("comportreader.classname");
oReadfromScanner2 = new ActiveXObject("comportreader.classname");
I am going to have up to 10 scanner readers which will update Flex client screen.
There will be many times when readers try to update the client in exact same time. What is a design pattern to manage simultaneous access to Flex? Or there will be no problem at all?
Thanks

Thanks for the feedback. This is still bothering me,
yes I could have a static RandomAccessFile and
synchronise on this, but I really want concurrent
access.
I've implemented a locking mechanism to prevent
different RandomAccessFile instances updating the
same record - is this not a waste if only one
RandomAccessFile can write to the file anyway?
Or is there another Java class I can use to access
the file in this way?
Thanks for the help.Hi,
if the intention of using multiple instanced of RandamAccessFile is concurrent access, then i feel your locking mechanism doesnt achieve the purpose..
also, at any case, you may not plan for full concurrency in updating a file....
it is more prone to malfunctions..
probably, to enhance performance, you can lock only the part your code that actually writes to the file, like io.write() , in this way you can perform all business logic with respect to writing and serialize only the actual file writing...
even in this case, you must be sure that writing to different part of the file, doesnt really impact other parts of the file which might be manipulated by other threads..
i have one more thought on this,
if updating different parts of the file doesnt affect content of other parts of the file,
then can you think of having different files itself?
if using different files is not a good idea, then
probably think of using some buffering mechanism, like collect all data concurrently and periodically update the actual file from the buffer.. just a raw idea but all depends on your system needs & requirements.. ..

Is Serialization a thread safe / concurrent access safe action?

Hi,
Is Serialization a thread safe / concurrent access safe operation? If not, how can one make sure a Serializable object won't be modified during the serialization process?
Thanks!

Jrm wrote:
Is Serialization a thread safe / concurrent access safe operation?Serialization is not inherently thread-safe. It is up to you to make it thread-safe.
If not, how can one make sure a Serializable object won't be modified during the serialization process?Control access to the objects you want to serialize so that no modifications occur during serialization.

Synchronized method not preventing concurrent access

Hi
I have 3 classes, T (a Runnable), TRunner (instantiates and starts a thread using T), and Sync (with one synchronized method, foo).
The problem is that foo is entered concurrently by different threads at the same time. How so?
T.java:
import java.util.Calendar;
class T implements Runnable
   private String name;
   public T(String name)
     this.name = name;
   public void run()
      Thread.currentThread().setName(name);
      Sync s = new Sync();
      System.out.println(Calendar.getInstance().getTime() + ".....Running " + Thread.currentThread().getName());
      s.foo(name);
}TRunner.java:
class TRunner
   public static void main(String args[])
       T tx = new T("x");
       T ty = new T("y");
       T tz = new T("z");
       Thread t1 = new Thread(tx);
       Thread t2 = new Thread(ty);
       Thread t3 = new Thread(tz);
       t1.start();
       t2.start();
       t3.start();
}Sync.java:
import java.util.Calendar;
class Sync
   public synchronized void foo(String threadname)
          System.out.println(Calendar.getInstance().getTime() + ":" + threadname + "....entering FOO");
          try
               Thread.sleep(5000);
          catch (InterruptedException e)
               System.out.println("interrupted");
          System.out.println(Calendar.getInstance().getTime() + ":" + threadname + "....leaving FOO");
}Console output:
C:\javatemp>java TRunner
Mon Apr 09 15:35:46 CEST 2007.....Running x
Mon Apr 09 15:35:46 CEST 2007:x....entering FOO
Mon Apr 09 15:35:46 CEST 2007.....Running y
Mon Apr 09 15:35:46 CEST 2007:y....entering FOO
Mon Apr 09 15:35:46 CEST 2007.....Running z
Mon Apr 09 15:35:46 CEST 2007:z....entering FOO
Mon Apr 09 15:35:51 CEST 2007:x....leaving FOO
Mon Apr 09 15:35:51 CEST 2007:y....leaving FOO
Mon Apr 09 15:35:51 CEST 2007:z....leaving FOO
C:\javatemp>Thanks in advance.

Only for static methods. For instance methods, the lock >is the object.You are absolutely right.
The Class object is no different from any other object. >"Entire" Class object makes no sense.What I wanted to say is that it's better to synchronize on the object we want to protect from concurrent access rather than on the entire class or instance object.
"Efficiency" is not altered by locking on a Class object vs. >any other object.I studied that it's better to synchronize on the objects we want to protect instead of the entire instance or class object. If one declares a method as synchronized, it means that other threads won't be able to access other synchronized methods for the same object, even if the two weren't in conflict. That was explained as a performance penalty.
>
Or when one or more threads may modify it and one or
more may read it.
Yep, sure.
>
No, they're not.
You are absolutely right. What I wanted to say is that local variables are unique per thread.
>
Local variables are unique per thread, but that's NOT
atomicity.Sorry for any confusion
Message was edited by:
mtedone

How many clients(specify in no.) concurrently access Weblogic server

hello
i want to know how many clients can concurrently access a application
server. for example:weblogic server or java webserver.

depends on your budget!!
You can go on increasing the number of clients by adding more WLS instances to a cluster. (and pay more licensing cost per node in the cluster).
You can also increase the number of clients by using expensive hardware. (Hp/Compaq/Sun/Dell) will be more than glad to sell you plenty of high-end stuff.
regards,
Abhishek.

Concurrent access

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