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Predicate Selectivity
Selectivity~~~~~~~~~~~文档 ID: 72539.1 68992.1Selectivity is a measure of the proportion of a row source retrieved by application of a particular predicate or combination of predicates.Within th...
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dump
事件说明例子Event 10013 - Monitor Transaction Recovery在Startup时跟踪事务恢复ALTER SESSION SET EVENTS '10013 trace name context forever, level 1';Event 10015 - Dump Undo Segment Headers-在...
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row cache lock与seq竞争
row cache lockoracle将数据字典存于sga内的行高速缓冲区（dictionary cache)内。行高速缓冲区位于共享池区域，可通过如下命令进行确认。sql> select pool,name,bytes from v$sgastatwhere name='row cache';想要修...
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Avoiding ORA-1555 Errors
Avoiding ORA-1555 Errors One of the most vexing problems that Oracle DBAs around the world face every day is this: ORA-1555: snapshot too old: rollback segment number 9 with name "R07" too small To...
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Parallel Execution Tuning
Parallel execution improves processing for:Queries requiring large table scans, joins, or partitioned index scansCreation of large indexesCreation of large tables (including materialized views)...
