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柱状图信息案例一则（1）
create table test_his as select * from dba_objects;--假设数据是09年全年的业务数据update test_his set created=to_date('2009-12-31','yyyy-mm-dd');commit;update test_his set created=CREATED-trunc(dbms_ra...
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连接取值
源于pub一个帖子：http://www.itpub.net/thread-1209587-1-1.htmlSQL> select object_id, 2 (select /*+USE_HASH(b c) FULL(C)*/ b.object_name 3&n...
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一则使用HASH技术进行优化的案例
表结构：create table test_key(pk varchar(32), key1 varchar(20), key2 varchar(20), key3 varchar(20), &nb...
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sql 语句中or条件之种种情况
1、相同字段or条件，转换为inlist 走index range scanSQL> select * from test_or a 2 where a.object_id=20 or a.object_id=21;执行计划----------------------------------------...
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jdbc row-prefetch 导致内存溢出
程序员反映说读取一个大对象时内存溢出故障现象是在rs.execute时就已经溢出了，还没到rs.getblob什么的之前分析jdbc时知道jdbc有fetch size，想到可能还会有prefetch让程序员设置相关jdbc参数再试，果然如此记录...
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特殊的游标泄漏问题
[php] con = DriverManager.getConnection(url);//获取数据库的元数据 dma =con.getMetaData();//将数据库中的表的名称转储出来 &nb...
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Avoiding fragmentation for ibm jvm
For a large Java? application, such as WebSphere? Application Server, the default kCluster space (for an introduction to kCluster, see Pinned clusters) might not be sufficient to allocate all classblo...
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Some basic heap sizing problems of ibm jvm
For the majority of applications, the default settings work well. The heap expands until it reaches a steady state, then remains in that state, which should give a heap occupancy (the amount of...
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minimum heap size for ibm jvm
When you have established the maximum heap size that you need, you might want to set the minimum heap size to the same value; for example, -Xms 512M -Xmx 512M. Using the same values is not usually a g...
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Frequently asked questions about the Garbage Collector
What are default values for the native stack (-Xss) and Java stack (-Xoss)? The Native stack size is machine-dependent, because it is based on the platform's C stack usage. The Java stack size is 400...
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Dynamic Sampling 两种方式的利弊
There are two ways to use dynamic sampling: TheOPTIMIZER_DYNAMIC_SAMPLING parameter can be set at the databaseinstance level and can also be overridden at the session level with theALTER SESSION co...
