2013年11月6日
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show current session id select sid from v$mystat where rownum=1;show blocking session select blocking_session,sid,serial#,wait_class,seconds_in_wait fromv$sessionwhereblocking_session is not NULLorder byblocking_session; 阅读全文
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Basic operationsu - oracle sqlplus / as sysdba show parameter background show parameteruser_dump_dest background_dump_dest: path_to_trace_file deadlook error code is:ORA-00060Refer to dead lock article http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:1528515465282one examp... 阅读全文
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问题 ThreadA invoke ThreadB, and then update DB ThreadB read DB, expect the update DB is finished by ThreadA But in some condition, Thread A update DB is slow, ThreadB have finished and update DB is not started.解决 UseReentrantLock 阅读全文
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引用 http://www.avricot.com/blog/?post/2010/05/03/Get-started-with-java-JVM-memory-(heap%2C-stack%2C-xss-xms-xmx-xmn...) -Xmx : max heap size (ex: -Xmx4g) -Xms : min heap size. (ex: -Xms2g) -Xmn : the size of the heap for the young generation Young generation represents all the objects which ... 阅读全文
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class MyResource implements Closeable{ @Override public void close() throw IOException{ }}try( myResource = newMyResource() ){ // no need to write finally block to release resource, java will automatially close this resource.}catch(Exception e){} 阅读全文
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问题 Dead lock in our App under some condition. Both database and application lock contributes to issue. The issue could be simplified to following model. Thread 1: Acquired DB Lock------------------||---------Try to get Application lockThread 2: Acquire Application lock------------||-----------Try .. 阅读全文
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引用文章Please refer to: http://coolshell.cn/articles/9606.html问题的症状从前我们的Java代码因为一些原因使用了HashMap这个东西，但是当时的程序是单线程的，一切都没有问题。后来，我们的程序性能有问题，所以需要变成多线程的，于是，变成多线程后到了线上，发现程序经常占了100%的CPU，查看堆栈，你会发现程序都Hang在了HashMap.get()这个方法上了，重启程序后问题消失。但是过段时间又会来。而且，这个问题在测试环境里可能很难重现。我们简单的看一下我们自己的代码，我们就知道HashMap被多个线程操作。而Java的文档说Hash 阅读全文