Check stuck thread in weblogic. e. . One socket reader thread is usually in the To run WebLogic Server in the 81-style-execute-queues mode, and be able to tune the thread count, an additional step is needed. 205. servlet. In order to get this fixed you are trying to increase the thread pool following the steps as per the document in the link below. The thread dump will be generated in the defined server stdout. If you have alarm from WLSDM stuck thread metric, follow the below instructions: · Quick health check of application server. 3) Optimize the program and reduce the processing time. This need not be changed usually. Increased Max Stuck Thread. Default (self StuckThreadMaxエラー. getState() print ‘Status of Jul 21, 2020 · When stuck thread increase in WebLogic Server alarm will be triggered. Gone is gone, end of story. [solution]: It can be solved by the following methods: 1) modify the stuckthreadmaxtime parameter, change the default 600s to 1200s, or other suitable values. Default execute queue from the Administration Console and reboot the server. admin) is aware that the thread has crossed 10 mins (600 sec = 10 min, not 15) This is a configurable value. Related questions. Download samurai which checks for the blocked threads , deadlock threads . Nov 25, 2014 · Weblogic monitors its threads and marks them as "stuck" after a certain period of time if they are not returning from a method like in a socket listener loop in thread's run method. If you want a thread to run till the server or application stops, you have to mark your class with a @LongRunning (weblogic. Aug 16, 2017 · HI All ,we are facing the thread stuck in the web logic frequently and we have to restart the planning services to resolve the issue. sh plugin from the Nagios XI server to your WebLogic server. In WL 8. ServletRequestImpl Jul 24, 2020 · Stuck threads will reduce the ebs performance and it’s very important activity to DBA’s. at the the time we can login to the particular warning server. To configure WebLogic Server stuck thread detection behavior. Note: This recommendation is highly application-dependent Jan 22, 2024 · Oracle WebLogic Server - Version 12. Here you can look at threads and identify stuck and hogging threads. 0 and later Information in this document applies to any platform. template. I suggest to investigate why the thread is taking so long and if it's possible to. for key in result: print (key + " has " + str (result [key]) + " stuck threads. we will get alerts. Stuck Thread Timer Interval: Enter the Dec 24, 2012 · Alternatively you can use something as simple as a http check on the port of the server to see if it responds. Cause: The number of threads assigned to this work manager has reached the configured value in the maximum threads constraint Feb 17, 2021 · redirect ('/dev/null','true') ## Print all server names and the number of stuck threads we counted per server. I tried to get the stuck thread count of To use user-defined execute queues in a WebLogic Server 10. 1. OBI 12C Weblogic and Em not opening. The stack-trace in the log file looks as follows: <Error> <WebLogicServer> <BEA-000337> <[STUCK] ExecuteThread: '12' for queue: 'weblogic. Jan 5, 2021 · In Weblogic, how can I change Work Manager's Stuck-Thread-Action using WLST and Jython. Make sure you export weblogic. It can simply takes a long time to execute the request. By Default, the WLS comes with 600 secs. The application is shutdown by bringing it into admin mode. Is there any way to kill these threads which got stuck? I don't want to hinder the activities of the users in another managed servers. Info: maximum thread constraint constraintName is reached Description: maximum thread constraint constraintName is reached. Apr 19, 2013 · at oracle. Is it possible to monitor web sessions and Stuck threads through the WebLogic Admin Console? Solution The execution time of SQL statement is too long. Default (self-tuning)' has been busy for "641" seconds working on the request Feb 21, 2014 · 2. WebLogic Server automatically detects when a thread in an execute queue becomes "stuck. Nov 26, 2011 · Does this message imply that my thread is aborted, or can it continue after this ? <[STUCK] ExecuteThread: '0' for q ueue: 'weblogic. Any help with the below is much appreciated. driver. Also, Windows XP is eol and you know it. WebLogic stuck thread protection. Select the Configuration -> Tuning tab in the right pane. – May 31, 2012 · Shut down the application if there are stuck threads in the application. No, you can't. 6 Information in this document applies to any platform. so at the end you will have a single log file which has around 20 - 25 seconds worth of action on the app server. This can be determined if you see the Nov 23, 2015 · WebLogic Console. 2. do", which is more than the configured time (StuckThreadMaxTime) of " 600" seconds Aug 3, 2023 · Oracle WebLogic Server - Version 10. 3. Services > Data Sources > EPMSystemRegistry > Configuration > Connection Pool. Stuck threads may result if the server is nearing out of memory. e stuck status=false like below. 5 to 10. – > Stuck Threads are only flags, there to warn you that this thread is taking too long. cmd or setDomainEnv. How to check Stuck Threads in logs – Doyensys Blog. For instance, the The first thing to check when there are Stuck Threads, is to generate a Thread Dump and analyze the threads that are being stuck. java:228) Maybe it is just the query which is taking more than StuckThreadMaxTime and WL issues a Warning. However, it also requires careful tuning to optimize its performance and avoid issues such as stuck threads, deadlocks, or memory leaks. OracleResultSetImpl. 0_80. Thread dumps show following stuck threads: Changes Cause . Feb 23, 2023 · Symptoms. 7. Aug 13, 2012 · The WebLogic Diagnostic Image includes a thread dump and can be automatically fired upon certain JMX metric thresholds being crossed by configuring a Watch and corresponding Notification in a WebLogic Diagnostic Framwork (WLDF) System Module that is targeted at your server. Default (self-tuning)’ has been busy for “631” seconds working on the request “weblogic. 0): setDomainEnv. Here check for “Heap Free Percent” (It should be more percentage free) Also, check for count of the “Hogging Thread Count” which should be either 0 or very less. xml file, setting the use81-style-execute-queues element to true. Your application threads are probably started like this: new Thread(new MyThreadClass())). from here. Select a discussion category from the picklist. This ensures that proxy and business services should not depend on the WebLogic Server execute thread pool for execution and WebLogic Server has enough free or idle threads to process any ad-hoc requests from Service Bus without leading to stuck thread problems. serverRuntime = getMBean('/ServerRuntimes/server1') Get the thread pool MBean: Next, you can use the getThreadPoolRuntime() method to get the MBean for the thread pool. If you have not already done so, stop the WebLogic Server instance. Oracle WebLogic Server - Version 12. If the server is close to out of memory, all requests should slow down. Worst case you have to give the customers/operators clear instructions how to gather dumps themselves to make them available to you. Default value for “StuckThreadMaxTime” is 10 minutes. Maximum Capacity: from 15 to 500. Then, explicitly create the weblogic. Step 2: if It will show the oacore server in “warning state” then we need to check. Jul 20, 2017 · A stuck thread does not always mean that the thread is waiting for something. on JDBC tab make sure all datasources are in RUNNING state. 0 Weblogic server tries to suppress current working thread and begins processing the new request. The only thing you can do is to figure if you can somehow detect such situations while they occur to then collect thread dumps and to log the results. 1. Goal. Increased database connection pool. So, you want the execute threads to be 4 + the number of stuck threads. I'm getting stuck threads intermittently in one of the managed servers. The following commands executed on your WebLogic server as the root user will do this: Aug 20, 2012 · You could use the weblogic. In you have stuck threads but the WebLogic Console is still available, you can go to Environment, Servers and select a server. answered Apr 21, 2015 at 21:32. ## Format for Nagios output etc. 163. You can try this feature in case it is available for Weblogic. Mark the server instance as failed and shut it down it down if there are stuck threads in the server. This is not intended to be a comprehensive guide to all Stuck Thread issues. Also weblogic won't consider a thread assigned to a long running task as being stuck. out in the Dec 22, 2019 · 3. lookup(TemplateRegistry:198), see dump below. x domain, you need to include the use81-style-execute-queues sub-element of the server element in the config. At the time of stuck threads. Firstly never troubleshoot stuck threads using only 1 dump, always take 3-4 dumps each spaced about 3-4 secs apart. Jun 13, 2016 · Is the client on Weblogic or the web service hosted on Weblogic or both? Can you check netstat -an | grep . If possible I would try: Find which query or queries are getting the threads stuck and check execution time. 3 Stuck Threads. it will give output like below. grep -i stuck logname. The timer starts when the thread begins processing the request within the server. Admin -url t3://weblogicadminconsoleurl:7001 -username username -password password THREAD_DUMP Weblogic Admin Console. For example, if we put maximim thread limit as 3, then if there are 10 parallel requests; 7 requests are in queue. For example you could use the nagios plugin check_http to check the status of a particular server. Sep 25, 2023 · warning Symptom{STUCK_THREADS,HIGH, ThreadPoolRuntime, ThreadPool has stuck threads} Weblogic Logs: <[STUCK] ExecuteThread: '7' for queue: 'weblogic. 問題: Account Reconciliation Managementが 「構成された時間 (StuckThreadMaxTime)」 を示すメッセージでタイムアウトします。. WebLogic Server is in unresponsive state and health of the server is in warning state. msgpack. To resolve an out-of-memory issue, see Section 24. 2. Aug 3, 2023 · In this Document. 11 1. WebLogic Server diagnoses a thread as stuck if it is continually working (not idle) for a set period of time. ") #11g #webcenter #weblogic #weblogic-portal. Namrta. Take 4 or 5 sets of thread dumps at an interval of 5 seconds between each. sh depending on the OS. This note is intended to be one example of how to identify the cause of a "STUCK" thread in the WebLogic Server or Managed Server. Admin url –: -username -password THREAD_DUMP. Jan 16, 2023 · Weblogic Admin utility. Before officially collecting garbage, GC will invoke the object's finalize (). The thread dump you have provided seems to be just fine, the one thread marked stuck seems to one where you are trying to uninstall a composite, something uninstall does take time and cause 1 thread to be stuck, this has Dec 26, 2012 · STUCK: A stuck thread is identified by Weblogic when it is taking more time than the configured stuck thread time (default is 600 seconds). In the body, insert detailed information, including Oracle product and version. " Because a stuck thread cannot complete its current work or accept new work, the server logs a message each time it diagnoses a stuck thread. WebLogic Serverは、設定した期間、作業状態が継続した(アイドルでない)場合、スレッドをスタック状態と診断します。 サーバーのスレッド検出動作は、スレッドがスタック状態と診断されるまでの時間や、サーバーがスタック・スレッドをチェックする頻度を Dec 25, 2020 · Is Weblogic 12c ThreadPoolRune JMX Counter available in Dyntrace v1. 0 and later: Frequent Stuck Threads In Imaging ExecuteThread: '31' for queue: 'weblogic. We are using weblogic 10. The long running task executed on timerExpired takes longer than the server wide StuckThreadMaxTime of 600 seconds. Cause. import thread import time def checkHealth(serverName): while 1: slBean = getSLCRT(serverName) status = slBean. You can read more about how weblogic 12 handles threads here: https://docs. Consider Paul's rocket mass heater . Jan 29, 2015 · Tuning = stuck thread reporting. i am trying to open weblogic and Em console and its keeps loading forever ( though it had opened few days before while May 17, 2017 · The weblogic console only shows threads that it (the weblogic server) created and therefore monitors. Oct 12, 2012 · If you see Stuck threads like below in the WebLogic server log then follow the steps mentioned to fix this issue. Also you can request a dump of the Thread stacks. Step 1: Go to the weblogic console and check for managed server status like oacore. Michel. ) called by other requests, these may be affected too. <Error> <WebLogicServer> <BEA-000337> < [STUCK] ExecuteThread: ‘1’ for queue: ‘weblogic. and it looks like Dyntrace doesnt see this in its Weblogic JXM editor WebLogic Server automatically detects when a thread in an execute queue becomes “stuck. Once installed you will also need to copy the check_wlsagent. May 15, 2020 · How Weblogic determine a thread to declare as hogging? A thread declared as Stuck if it runs over 600 secs (default configuration which you can increase or decrease from admin console). In this post I will deconstruct this thread and describe the data it contains and the potential issues it may illuminate. In between the refresh actions, identify the threads that are still executing the same request (slow running threads). This document provides comprehensive guidance on how to tune WebLogic Server parameters, monitor its health, and troubleshoot common problems. One thread dump is not enough to analyze the problem. In work load tab make sure pending requests are not too many, else you need to look at the number of work managers and there health and work done. By default, WebLogic Server considers a thread to be "stuck" after 600 seconds of continuous use. 3. Default (self-tuning)' has been busy for "609" seconds working on the request "Http Request: /getSunPayment. A thread might get stuck due to various reasons. Click on Environment --> Servers --> Managed Server --> Monitoring --> Performance. Edit the config. All Work Managers belonging to the application are shut down, and behave as described above. 21. First, set the use81-style-execute-queues element to true in the configuration file. Third, Check the Performance and Thread of the Managed Server. Dec 15, 2017 · In general no, but if for example the stuck thread is holding a lock on an object (database, file, etc. Default (self-tuning)' has been busy for "zzz" seconds working on the request "-----" , which is more than the configured time Oracle WebLogic Server is a powerful and scalable application server that can run various applications and services. Take several thread dumps to check what threads are doing. Stuck Threads are threads that are blocked, and can't return to the threadpool for a certain amout of time. The queue monitors throughput over time and based on history, determines whether to adjust the thread count. extensions. In WL 9 and 10, WebLogic allocates 33% of server threads to act as socket readers by default. Tuning the Execute Thread Detection Behavior. Symptoms. The definition of "world" depends on the garbage collector being used and context. Expand Environment and click on Servers in the left menu; Click on the Admin server or any managed server you want to check the stuck threads; Click on the Monitoring tab in the server properties; click on WebLogic Server automatically detects when a thread in an execute queue becomes “stuck. 4 Aug 7, 2023 · Oracle WebLogic Server - Version 12. By Default, the WLS For example, if you have four processors, then four threads can be running concurrently with the number of stuck threads. If a request is taking longer than 10 minutes, the stuck thread is reported to Oracle WebLogic Server server_name. Now you can go to Monitoring, Threads. Can anyone please help me in understanding, why thread dump does not get generated from console and Why I am getting the message saying server must be running. connector. As per my best knowledge you cannot do it without re-boot . ). rnel. 20201201-130524 . Changes. 12. ADF application is deployed in this cluster. 1, there are 3 socket reader threads by default. i. This will put minimal load on the server. For example, if historical throughput statistics indicate that a higher thread count increased throughput, WebLogic increases the thread count. 0 and later: Stuck Threads Issue in WebLogic. There could be situations where these the requests waiting in queue could take up to 30-40 minutes to be Oracle Business Intelligence. (StuckThreadMaxTime) of “600” seconds in “server-failure-trigger”. We're confident our code did not introduce this issue since, in the example above, it's clear we're using Apr 8, 2022 · I think this will cause weblogic to create a new thread for the task instead of taking a thread from the work manager thread pool. then check for the blocked threads or any deadlock threads. Similarly, if statistics indicate that fewer threads did not reduce throughput, WebLogic Apr 9, 2019 · 1. I have recently configured obi 12c application ver. My Oracle Support provides customers with access to over a million knowledge articles and a vibrant support community of peers and Oracle experts. Otherwise, you might have to use your own custom-built OneAgent extension. jdbc. It cannot do so, the message is only a status info so that you (i. set StuckThreadMaxTime with bigger value (its placed on weblogic console in: domain > Environment > Servers > Admin Server > Configuration/Tuning) edited Mar 11 Jul 1, 2018 · 0. On EBS 12. You can tune a server’s thread detection behavior by changing the length of time before a thread is diagnosed as stuck, and by changing the frequency with which the server checks for stuck threads. For example, if you have four processors, then four threads can be running concurrently with the number of stuck threads. 24. It notifies and attaches thread dump. EDITED: Another solution which is useful when you are trying to read from a socket and you are not getting any response from the server is the following: An RMISocketFactory instance is used by the RMI Work Manager minimum and maximum constraints should be set based on the maximum load. Feb 12, 2016 · 1. During a GC sweep, the GC will "stop the world" to perform its cleanup. Also, consider setting the WebLogic Server “Stuck Thread Max Time” value from its default 600 seconds to a larger value such as 1200 seconds. For example, the following thread is stuck waiting to process POST data: Cause Nov 26, 2011 · I've got the below code working on Weblogic Application Server 10. Default (self-tuning)' has been busy for "626" seconds working on the request "Workmanager: default, Version: 0, Scheduled=false, Started=true, Started time: 626850 ms", which is more than このエラーは、WebLogic Server で「Stuck Thread Max Time:」のデフォルト値 600 秒を超過したために発生します。 回避方法: コンフィギュレータが応答しない場合は、再起動します。WebLogic Server の「Stuck Thread Max Time」値をデフォルトの 600 秒から 1200 秒などもっと Mar 21, 2019 · 0. internal. Aug 17, 2011 · In threads tab make sure health is OK and there are no stuck threads i. To launch a long running task, you need to set the LONGRUNNING_HINT to true in the ManagedTask that is launched. Potentially, you could go to the weblogic admin console and restart the application. When the system is under stress, STUCK threads are seen in WebLogic logs at regular intervals. ' to get the hung threads for the traditional WebSphere. References. For example: When large BI report is running and the time it Nov 6, 2009 · We are able to configure by using "Work Managers" in WebLogic and putting a limit on the number of threads for that servlet. 0 with two domains. ” Because a stuck thread cannot complete its current work or accept new work, the server logs a message each time it diagnoses a stuck thread. Dec 8, 2017 · For better clarification: BEA-002936. Mar 8, 2024 · Oracle WebCenter Content: Imaging - Version 12. start(), this does not use any weblogic API and are unknown to it. Servers -> Some_Server -> Configuration -> Tuning -> Stuck Thread Max Time This will check on the Stuck Thread Timer Interval for any and all stuck threads and report it in the log file for the server like: 'WebLogic. You can configure Node Manager or a third-part high-availability solution to restart the server instance for automatic failure recovery. In this video, we will cover Troubleshooting of weblogic server, running with Warning HealthCheckout my below videos as well :Weblogic HTTP Extended Logging Jan 8, 2012 · There are many ways to do that. If some thread doesn't return in 600 secs, It gets a flag 'stuck thread'. Then you should look for you want to check is a stuck thread or long running Apr 19, 2011 · 1. When facing slowdown conditions, you will normally see May 10, 2023 · In this Document. kernel. Dec 16, 2023 · Click to get started! In this Document. Stuck Thread Max Time: Enter the number of seconds, that a thread must be continually working before this server diagnoses the thread as being stuck. xml file and reboot the server. One of the them is working fine. Mar 17, 2022 · It seems you are looking for the hung threads. 4. com Aug 18, 2023 · Oracle WebLogic Server - Version 12. Aug 31, 2012 · outputStream. You have two options: make processing faster. If the Configurator does not respond, restart it. Apr 24, 2013 · You can access the thread pool health details using WLST (WebLogic Scripting Tools) scripts (if you are familiar with Python, it should not be a problem), or by accessing JMX counters using Java. Mar 16, 2012 · After that change the Weblogic system status is complaining about the thread pool "Thread pool has stucked threads". just drap the thread dump file into the samuria console . OS: Centos Weblogic: WebLogic Server Version: 10. Apr 26, 2010 · Weblogic does NOT kill stuck threads after the StuckThreadMaxTime. This post contains a sample script that sends an alert email whenever stuck threads exist, and in the comments section you will find some samples of Dec 14, 2019 · WebLogic Stuck Threads: Understanding Hogger and Stuck threads Stuck Threads are threads that are blocked, and can’t return to the threadpool for a certain amout of time. next(OracleResultSetImpl. We need to monitor stuck thread count. Solution. Mar 9, 2023 · This MBean provides information about the server’s state and performance, including information about threads. Possibly due to stuck threads. It may be a small cluster of threads or all of them. To determine the amount of stuck threads, see Tuning the Execute Thread Detection Behavior. Use the WebLogic Console to change this value (base_domain > Environment > Servers > Admin Server > Configuration/Tuning). Send a SIGQUIT, either via CTRL + \ ( CTRL + Break on Windows) or with a kill -3 <pid>. * Stuck Thread Timer Interval: Enter the number of seconds, after which WebLogic Server periodically scans threads to see if they have been continually working for the length of time specified by Stuck Thread Max Time. oracle. LongRunning Dec 16, 2023 · Click to get started! My Oracle Support provides customers with access to over a million knowledge articles and a vibrant support community of peers and Oracle experts. If all application threads are stuck, a server instance marks itself failed, if configured to do so, exits. You can try WLSDM. We are seeing server overloading (network IO), admin inaccessible errors. Use WLST and threadDump() The first option has usually my preference. May 17, 2009 · Socket Reader Threads accept the incoming request from the Listen Thread Queue and put it on the Execute Thread Queue. One set of thread dumps alone wont be too helpful to get to the root cause. If you need to script some kind of monitoring tool, WLST is extremely powerful. 0 version and JDK 1. NOTE: Server is in running state. Due to this issue, users see a lot of performance issues and sometimes cannot even access the EBS instance when this issue Jul 28, 2015 · If WL console is unresponsive then it means that you Admin server thread is stuck, so you need to kill you Admin server Java process and restart it . TemplateRegistry. x find that some or all the OACore Managed servers are frequently going into Warning status with struck threads. Login to weblogic admin console with admin credentials. 6 and later: How Stuck Thread Timeout and JTA timeout values are related? Mar 5, 2024 · Oracle WebLogic Server - Version 12. we can see the servers are in warning state. Mar 11, 2016 · 3. 解決策: 次の手順に従って、「スタック・スレッド最大時間」設定の値を大きくします: WebLogicコンソールにログオンします If the WLSAgent cannot be used then NCPA will need to be installed on the WebLogic server as per the Installing NCPA documentation. flush(); The problem we're seeing in WebLogic is lots of STUCK threads, so we dumped the thread stack and found some threads getting stuck at org. Oracle WebLogic Server - Version 10. Mar 12, 2019 · In this post, we are going to share the Weblogic WLST Stuck Thread Monitoring Script which will trigger an email notification and create heap and thread dumps when the maximum Thread stuck count has reached the threshold. rmi. Also, depending on what the stuck thread is doing, it may use excessive resources (cpu, memory, disk, etc. Becouse your processing takes 20min and default setting of StuckThreadMaxTime is set to 600 seconds, you will see such errors in logs. Stuck Thread Handling WebLogic Server checks for stuck threads periodically. ke. Check JMS connections are not too high. Problem. I'm using WebLogic 11g. Then take the decision according to it. “StuckThreadMaxTime” parameter). Problem can happen any time and any load condition, with no pattern to the occurrences. Scenario 1: Every alert we need to check the log file and investigate based on Jul 10, 2018 · I could see the health show "Warning" and the reason "ThreadPool has stuck threads". Stuck Thread. but the 2nd one. Note that it is possible that some of your threads are doing legitimate work for over 10 minutes with Mar 27, 2020 · # Node Manager needs to be running to run this script. 2) Increase the number of threads to prevent thread blocking. 6 and later: Stuck Threads in WebLogic Server. 0. clientTimeout setting in order to avoid thread stuck situations when the target server is experiencing problems. To determine the amount of stuck threads, see Detecting "Stuck" Threads. I do not w To use user-defined execute queues in a WebLogic Server 10. '19' for queue: 'weblogic By default, WebLogic Server considers a thread to be "stuck" after 600 seconds of continuous use. We are facing issue in our production environment with multiple blocking threads and while checking the thread dumps have found the below stack trace where in 14 blocking threads were present with same description. Check if the finalizer thread is blocked or waiting. From a command line or shell, a thread dump can be generated via the following command (deprecated from WLS 9. I've done some changes as per some blogs suggest: 1. Mar 8, 2016 · But, when I try to generate thread dump using kill -3 <PID>, it gets generated. Login into WebLogic admin console; Navigate to Server > Monitoring > Threads > Dump Thread Stacks; WLST Aug 15, 2011 · 8. 6. We are using a builtin feature ' Use JMX/PMI extension editor to add custom metrics without coding. Jun 29, 2018 · One way to check if you have stuck threads is through Weblogic Admin console. java weblogic. jar in your path; Execute a command on UNIX session: java weblogic. Jan 15, 2019 · The following thread was extracted from a thread dump taken on a JVM instance running WebLogic Server. Use jstack <pid> (or jstack -F <pid> if the process is hung) Use VisualVM. Enter a title that clearly identifies the subject of your question. Does it show the sockets in ESTABLISHED state? or some other state like TIME_WAIT or CLOSE_WAIT ? How long have you configured your stuck-thread-timeout? The default is 600 seconds, so does this operation take longer than 10 minutes? Sep 3, 2013 · Refresh the page every 3-5 seconds. It could be that the stuck threads are generated by a problem in the code, by the unavailability of an external system, or it can even be expected behavior, in the case of some long-lasting operations in the Nov 7, 2016 · I'm having a Weblogic server with one Admin Server and 3 managed servers in a single cluster. Jul 5, 2017 · 3. May 13, 2018 · An execute thread is classified as STUCK when the thread is stuck working on a request for more than the configured stuck thread maximum time (i. Note: This recommendation is highly application-dependent. or ln bc xy ou hd yf pu cj mb