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ASM知识点(转载)
ASM知识点 • Automatic Storage Management• Oracle10g New Feature• 每个机器上允许一个ASM实例• 不支持的文件类型– 操作系统文件（非数据库相关）– Oracle Binaries, trace files – Voting Disk– OCRASM支持单实例数据库写入无序，读取有序ASM提供了3种冗余方法。external redundancy表示Oracle不帮你管理镜像，功能由外部存储系统实现，比如通过RAID技术。normal redundancy（默认方式）表示Oracle提供2路镜像来保护数据。high redundancy表示Oracle提供
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ASM process设置
Processes = 25 + (10 + [max number of concurrent database file creations, and file extend operations possible])*n n is the number of RDBMS instance (ASM clients) connecting to ASM The source of concurrent file creations can be any of the following:1. Several concurrent CREATE TABLESPACE commands2. Creation of a partitioned table with several tablespace creations3. RMAN backup channels4. Concurrent archive log file creations[@more@]
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跟老美真难沟通...
传说中的奥运购票系统,老美设计的数据库,性能我就不想说什么了.在j仅30万并发注册情况下的等待事件...Top 5 Timed Events EventWaitsTime(s)Avg Wait(ms)% Total Call TimeWait Classenq: US - contention353,36610,2192939.0Otherenq: SQ - contention2,3965,4532,27620.8Configurationlog file sync187,8404,0582215.5Commitrow cache lock8,8522,0872368.0Concurrencybuffer busy waits76,3881,920257.3Concurrency很明显的undo问题，热点块。。。跟老美交流居然说一点问题没有，我晕[@more@]
